FOREWORD. (This foreword is not part of this standard.)

Transcription

1 FOREWORD (This foreword is not part of this standard.) This document is a TIA/EIA Telecommunications standard produced by Working Group TR of Committee TR-41. This standard was developed in accordance with TIA/EIA procedural guidelines, and represents the consensus position of the Working Group. Some of the requirements contained in this standard are based on information obtained from external organizations, including Bellcore, Stentor, ANSI, and others. The Working Group gratefully acknowledges the cooperation and support of these external organizations. Annex A lists references that are informative only, and is not considered a part of this standard. Suggestions for improvement of this standard are welcome. They should be sent to: Telecommunications Industry Association Engineering Department Suite Wilson Boulevard Arlington, VA 22201

2 TR Working Group Members CONTRIBUTOR ORGANIZATION REPRESENTED James Bress -...AST Technology Labs David Stenner -...Advent Instruments Trone Bishop -...Bell Atlantic John Balinski, Hala Mowafy, Stan Pietrowicz -...Bellcore Tom Beason, Dennis Dease -...BellSouth Jim Mazzolini, Mark Karnowski -...Casio-Phonemate Harry Lewis, Mark Mutz -...CIDCO Phil Holland -...Circa Communications Thomas Ahn -...Cobra Electronics Dr. Norman Beamish -...Conexant System Doug Kolb, John Riley -...DSP Software Engineering Howard Jelinek -...Electronic Design Associates Harry Van Zandt -...GTE Scott Roleson -...Hewlett Packard Scott Early -...InDesign Michael Christensen -...Industry Canada Bob Brady -...Intelidata Ron Bernot, Clifford Jones -...Intertek Testing Services Philip Ching -...Mitel Semiconductor Division Greg Brauns -...Mitsubishi Electric Dave Kolkman -...Motorola (SPS) James Kemerling -...Mx-Com Len Bleile, Roger Britt, Jerry Freestone -...Nortel Networks Greg Neal (Editor) -...Notify Corp. William Becker, Steve Whitesell -...Lucent Technologies Inc. LeRoy Baker -...RELTEC Heather Poggi-Mannis -...Rochelle Communications Koji Arata, Herbert Lippold -...Sanyo Fisher Co. Ron Magnuson -...Siemens Tim Capizzi, Yoshi Nogami -...Sony Dr. Amar Nath Ray, Cliff Chamney -...Sprint Local telephone Division John Dabnor, Moshe Kuperschmidt -...Tadiran Telecommunications Frank Banul -...Texas Instruments Don McKinnon -...Thomson Consumer Electronics Michael Menard, Russ Stubbs-...US West Al Baum -...Uniden Dean McCullough, Steve Kropp, Chris Schatz -...Vtech Engineering Larry Bell -...Wyle Labs Stephen Zmina -...Zilog Tom Russell -...Chairman, TR41.3.1

3 TIA/EIA PN-4078 (To become ANSI TIA/EIA ) Telecommunications Telephone Terminal Equipment Type 2 Caller Identity Equipment Performance Requirements Formulated under the cognizance of TIA Engineering Committee TR-41 User Premises Telecom Requirements

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5 TABLE OF CONTENTS 1. SCOPE 1 2. NORMATIVE REFERENCES 1 3. ABBREVIATIONS, ACRONYMS, AND DEFINITIONS ABBREVIATIONS AND ACRONYMS DEFINITIONS TECHNICAL CRITERIA FOR TYPE 2 CPE MANDATORY, RECOMMENDED, AND PERMISSIVE CRITERIA GENERAL FUNCTIONALITY CAS DETECTION CAS Detector Performance Recommendations CAS Recognition CAS Recognition Parameters CAS Recognition Test Matrix Talkdown Performance Parameters Talkoff Performance Parameters Muting Talkoff ADJUNCT SERIES IMPEDANCE REQUIREMENTS AC Impedance DC Impedance CAS-ACK HANDSHAKE AND MULTIPLE EXTENSION INTERWORKING User s Perspective MEI Functions Line and CPE States Determination of the ACK-Sender Determination of the Backup ACK-Sender CAS-ACK Handshake Protocol ACK Signal Generation Voicepath Mute Control Inter-CPE Signaling Request to Flash Signaling Request to Flash Signal Generation Request to Flash Signal Detection and Response Type 3 Assertion Signaling Type 3 Assertion Signal Characteristics Type 3 Assertion Signal Detection and Response TYPE 2 FSK SIGNAL PROPERTIES Page i

6 4.7.1 Frequency Signal Levels Twist Baud Rate Noise Test Matrix for the FSK Signal Properties, Including Multiple Impairments MESSAGE PREAMBLE MESSAGE FORMATS Binary & ASCII encoding Message Types Message Length Parameter Types Parameter Length Mark Bits Checksum Markout DATA FIELD DEFINITIONS MDMF Date and Time Parameter Calling Number MDMF Calling Number Parameter MDMF Dialable Directory Number Parameter MDMF Reason for Absence of Calling Number Parameter Calling Name MDMF Calling Name Parameter MDMF Reason for Absence of Name Parameter MDMF Call Qualifier Parameter MDMF VMWI Parameter Reason for Redirection Parameter (Reserved) EXCEPTION HANDLING Checksum Error No Data Detected Out of Range data LINE INTERFACE ANNEX A INFORMATIVE REFERENCES ANNEX B INFORMATIVE DIAGRAMS Page ii

7 LIST OF FIGURES Figure 1 - CAS-ACK Handshake Diagram 16 Figure 2 - CPE state generating RTF, multiple CPE Off-Hook, successful synchronized Flash 18 Figure 3 - Line state during RTF, multiple CPE Off-Hook, successful synchronized Flash_18 Figure 4 - Line state during RTF, single CPE Off-Hook 18 Figure 5 - CPE state generating RTF, multiple CPE Off-Hook, unsuccessful RTF 19 Figure 6 - Line state during RTF, multiple CPE Off-Hook, unsuccessful RTF 19 Figure 7 - CPE state detecting and responding to an RTF, successful synchronized Flash 19 Figure 8 - Line state during RTF, Multiple CPE Off-hook, successful synchronized Flash _20 Figure 9 - CPE state detecting & responding to an RTF, unsuccessful RTF 20 Figure 10 - Line state during RTF, multiple CPE Off-Hook, unsuccessful RTF 20 Figure 11 - Line state during Type 3 Assertion, multiple CPE Off-Hook 21 Figure 12 - Signal-to-Noise Accept Parameters 22 Figure 13 - MDMF format 26 Figure 14 - MDMF Date and Time parameter 29 Figure 15 - MDMF Calling Number Parameter 30 Figure 16 - DDN Parameter 31 Figure 17 - MDMF Reason for Absence of Calling Number Parameter 31 Figure 18 - MDMF Calling Name Parameter 32 Figure 19 - MDMF Reason for Absence of Name Parameter 33 Figure 20 - MDMF Call Qualifier Parameter 33 Figure 21 - MDMF Visual Message Waiting Indicator Parameter 34 Figure 22 Example of a possible sequence for an MEI event 37 Page iii

8 LIST OF TABLES Table 1 - CAS Parameter Limits 6 Table 2 - Group 1, CAS Recognition - All Parameters at Nominal Values 7 Table 3 - Group 2, CAS Recognition - One parameter at a time at the extreme value 7 Table 4 - Group 3, CAS Recognition - Parameters at 90% from Nominal, CAS 75.5ms 8 Table 5 - Group 3, CAS Recognition - Parameters at 90% from Nominal, CAS 84.5ms 9 Table 6 - Group 4, CAS Reject Amplitude 10 Table 7 - Group A, Variable Level Sensitivity Tests 23 Table 8 - Group B, Twist Test - Nominal Otherwise 23 Table 9 - Group C, Combined Impairments - Frequencies, Baud, and Twist 24 Table 10 - Group D, Out-Of-Band Noise Tests 25 Table 11 - Group E, In-Band Noise Tests 25 Table 12 - Message Type Values 27 Table 13 - Parameter Type Values 27 Page iv

9 1. SCOPE This standard addresses the technical issues associated with Type 2 Caller Identity Customer Premise Equipment (CPE) for Off-Hook signaling used with Call Waiting to send data frames packaged in Multiple Data Message Format (MDMF). Specifically, this standard establishes formal criteria for the signals and protocol that the CPE should be capable of receiving. It incorporates by reference TIA/EIA 716, which defines the On-Hook signaling and protocols that must also be supported by Type 2 CPE. This standard is not in any way intended to be a guideline for switch suppliers or a Network Interface requirement. 2. NORMATIVE REFERENCES The following standards contain provisions which, through reference in this text, constitute provisions of this standard. At the time of publication, the editions indicated were valid. All standards are subject to revision, and parties to agreements based on this standard are encouraged to investigate the possibility of applying the most recent editions of the standards indicated below. ANSI and TIA maintain registers of currently valid national standards published by them. 1) ANSI T , American National Standard for Telecommunications - Interface between Carriers and Customer Installations - Analog Voicegrade Switched Access Lines Using Loop-Start and Ground-Start Signaling. 2) ANSI/TIA/EIA-470-B-1997, Telecommunications - Telephone Terminal Equipment Performance and Compatibility Requirements for Telephone Sets with Loop Signalling. 3) ANSI/TIA/EIA , Telecommunications - Telephone Terminal Equipment Type 1 Caller Identity Equipment Performance Requirements. 4) Bellcore GR-30-CORE, Issue 2, December 1998, Voiceband Data Transmission Interface. 5) Bellcore SR-3004, Issue 2, January 1995, Testing Guidelines for Analog Type 1,2, and 3 CPE as Described in SR-INS ) Bellcore SR-INS , Issue 1, August 1993, Classes of Customer Premises Equipment 7) Bellcore SR-TSV , Issue 1, December 1992, (plus Bulletin No. 1, September 1993), Customer Premise Equipment Compatibility Considerations for the Voiceband Data Transmission Interface 8) CCITT Recommendation P.56 - Objective Measurement of Active Speech Level, CCITT Blue Book, Volume V Telephone Transmission Quality, 1989 Page 1

10 3. ABBREVIATIONS, ACRONYMS, AND DEFINITIONS 3.1 Abbreviations and Acronyms For the purposes of this Standard, the following abbreviations and acronyms apply. ACK: ACKnowledgment Signal ADSI: Analog Display Services Interface CAS: CPE Alerting Signal CIDCW: Calling Identity Delivery on Call Waiting CWD: Call Waiting Deluxe CPE: Customer Premises Equipment DDN: Dialable Directory Number. FSK: Frequency Shift Keying MDMF: Multiple Data Message Format MEI: Multiple Extension Interworking RTF: Request-to-Flash SAS: Subscriber Alerting Signal VMWI: Visual Message Waiting Indicator. 3.2 Definitions For the purposes of this Standard, the following definitions apply. ACK-Sender: The single CPE that will complete the CAS-ACK handshake and terminate the line during data transmission if no incompatible extension is detected. ACK Signal: The signal used by a CPE to ACKnowledge the receipt of a CAS. Back-up ACK-Sender: The single CPE that will complete the CAS-ACK handshake and terminate the line during data transmission if no ACK-Sender is present. Checksum: The last byte of an MDMF message used as a simple method for the detection of errors. It is calculated as the 2 s complement of the modulo 256 sum of all bytes in the MDMF message from the Message Type to the last Parameter Word. CPE Alerting Signal: The signal that informs the Type 2 CPE that there is a Call Waiting. CPE State: The condition of the telephone device. It can be either On-Hook or Off-Hook. Flash: A Line High condition generated by CPE, lasting from 300 ms to 1000 ms, used as a signal to the Central Office switch. Line State: The condition of the tip and ring interface. It can be either In-Use or High. Page 2

11 Listening-Path: The path from electrical signals at Tip & Ring to acoustic signals at the CPE receiver/speaker. Mark: A logical 1 for FSK signaling. Message Length: The second byte in an MDMF message that indicates the length of the MDMF message (in bytes) excluding the Message Type byte, Message Length byte, and the Checksum byte. Message Type: The first byte in an MDMF message used to indicate the type of message. Multiple Extension Interworking: The ability to receive Caller ID information with multiple CPE Off-Hook on the same line. Parameter Length: The second byte in a Parameter Message that indicates the length of the Parameter Message excluding the Parameter Type byte and the Parameter Length byte. Parameter Message: A block of bytes which starts with a Parameter Type and ends with the last Parameter Word for the given Parameter Message. Parameter Type: The first byte in a Parameter Message that indicates the type of the Parameter Message. Parameter Word: Each data byte which follows the Parameter Type byte and Parameter Length byte in a Parameter Message up to the next Parameter Type byte or Checksum. Request-to-Flash: A timed DC signal that is used to modulate the DC line voltage to signal an attempt to orchestrate a synchronized period where all CPE proceed to the On-Hook state to generate a flash signal. Space: A logical 0 for FSK signaling. Subscriber Alerting Signal: A signal that informs the customer that there is a Call Waiting. Talking-Path: The path from acoustic signals at the CPE microphone to electrical signals at Tip & Ring. Twist: 1) The power differential of the Mark and Space signal amplitudes for FSK signals. FSK Twist is positive when the Mark signal amplitude is higher than the Space signal amplitude. 2) The power differential between tones of a dual tone signal (e.g. CAS). Dual tone Twist is positive when the lower frequency tone amplitude is greater than the higher frequency tone amplitude. Type 3 Assert Signature: A DC signal used to modulate the DC line voltage to signal the current ACK-Sender to relinquish its role as ACK-Sender. Voicepath: Collectively consists of a Talking-path and a Listening-path. Page 3

12 4. TECHNICAL CRITERIA FOR TYPE 2 CPE 4.1 Mandatory, Recommended, and Permissive Criteria Three types of criteria are specified in this standard; Mandatory, Recommended and Permissive. Mandatory criteria are designated by the terms shall and shall not. These criteria are used to indicate requirements for which no deviation is permitted. Recommended criteria are designated by the terms should and should not. These criteria are used to identify compatibility or performance advantages towards which future designs should strive. Permissive criteria are designated by the terms may and need not. These criteria are used to identify an action that is permitted within the limits of the standard. 4.2 General Type 2 Customer Premises Equipment (CPE) include all the On-Hook functionality of Type 1, with the addition of supporting Off-Hook signaling associated with Calling Identity Delivery on Call Waiting (CIDCW). In the Off-Hook state, a Type 2 CPE shall be capable of detecting a special dual tone signal known as the CPE Alerting Signal (CAS), completing the handshake sequence preceding data communication, and decoding data frames packaged in MDMF. In the On-Hook state, Type 2 CPE shall meet all the criteria for Type 1 CPE given in TIA/EIA Functionality Type 2 CPE are required to perform eight major functions: 1) The CPE shall possess the capability to detect the CAS. The detection takes place in an environment that may introduce speech, noise and other interfering signals. 2) The CPE shall be able to detect a non-compatible Off-Hook CPE. 3) The CPE shall be able to perform the roles of ACK Sender and Backup ACK Sender. 4) The CPE shall be able to mute the voicepath and send an acknowledgment signal (ACK) to indicate that it received the CAS successfully and is ready to receive data. 5) The CPE shall be able to detect and decode the Frequency Shift Keying (FSK) data in both on-hook and off-hook states. 6) The CPE shall be able to detect the Request-to-Flash (RTF) signal and respond appropriately to generate a synchronized Flash. 7) The CPE shall be able to generate an RTF signal.. 8) The CPE shall be able to detect a Type 3 Assertion signal and respond appropriately. 4.4 CAS Detection There are three aspects to defining CAS detection performance: 1) Signal recognition, 2) Talkdown performance and 3) Talkoff performance. 1) CAS recognition establishes the ability of the CPE to detect the CAS over the range of expected signal parameters in the absence of speech or noise. Page 4

13 2) CAS talkdown performance establishes the ability of the CAS detector to detect CAS in the presence of speech, music, and noise. The ability to detect CAS in the presence of interfering signals is necessary for proper operation with CIDCW. Although the far-end will be muted during transmission of the CAS, near-end signals may potentially corrupt the CAS and impede its detection. 3) CAS talkoff performance establishes the ability of the CPE to resist CAS imitations produced by speech, music, and noise. Distinguishing between legitimate CAS and those simulated by interfering signals is important for services like CIDCW. Falsely detecting a CAS simulated by interfering signals will result in undesirable breaks in the voicepath, which will adversely affect telephone service quality. Robust CAS performance is necessary because a CAS detector constantly monitors the line and is exposed to both near-end and far-end signals CAS Detector Performance Recommendations The CAS detector performance criteria set forth in this document reference the test plan described in Bellcore documents SR-TSV and SR This test plan attempts to model the real world environment and provides talkoff and talkdown performance measurements consistent with expected field performance. The test plan makes use of statistical information gathered from various field studies about the environment in which CAS detectors are expected to be used. Particularly, the test plan relies upon information about loop loss distribution, near-end speech level distribution, and far-end speech level distribution. The test plan employs these distributions to weight CAS detector performance according to the probability that certain combinations of speech levels and loop losses occur. The weighted performance values are then calculated as described in Bellcore SR- TSV to provide estimates of overall CAS detector performance. Performance objectives have been established for the average case, the worst 1% of all combinations and the global 100% case. Power levels of signals are expressed as power per tone, in dbm referenced to a 600 ohm termination. Speech levels are expressed as the Active Speech Level (ASL), in dbm, and measured according to Method B of CCITT Recommendation P.56. Signal-to-speech power ratios are expressed in db, corresponding to the per-tone signal power in dbm minus the active speech level in ASL-dBm. Talkdown and talkoff testing as described in Bellcore SR-TSV uses the 97.6 hour standard speech test library contained in the Telcordia Technologies (formerly Bellcore) Licensed Product, LP-B17, Speech Test CD Set for Type 2 and 3 Customer Premises Equipment. 1 1 LP-B17, Speech Test CD Set is a licensed product supplied by Telcordia Technologies (formerly Bellcore). This information is given for the convenience of users of this Standard and does not constitute an endorsement by ANSI/TIA of the product named. Equivalent products may be used if they can be shown to lead to the same results. Page 5

14 4.4.2 CAS Recognition The CAS is a dual tone signal nominally 80 ms in duration. Table 1 defines CAS parameter detection limits. These limits reflect severe combinations of switch, digital loop carrier, and loop plant variables. Signals outside these limits may be either accepted or rejected by the CAS detector CAS Recognition Parameters The CPE shall detect all CAS satisfying the signal characteristics defined in the following table: Table 1 - CAS Parameter Limits Parameter Value Lower Tone Frequency 2130 Hz ± 0.5% Upper Tone Frequency 2750 Hz ± 0.5% Dynamic Range (dbm per tone) -14 to -32 dbm Power Differential within Dynamic Range (Twist) ± 6 db Signal Duration ms Twist is defined as the signal level differential between the lower and upper tones. Twist may be negative (when the amplitude of the lower frequency tone is lower than the amplitude of the higher frequency tone) or positive (when the amplitude of the higher frequency tone is lower than the amplitude of the lower frequency tone). The CPE shall be capable of detecting CAS with +/- 6 db of Twist. The CPE shall reject all CAS below -45 dbm per tone. Detection of the CAS by the CPE shall not be impaired by the presence of any normal or distinctive Subscriber Alerting Signal (SAS). Refer to the Call Waiting (CW) Signal chart in ANSI T1.401 for further details on the SAS alert tones. For testing purposes, the source impedance of the signal generator shall be 900 ohms. CAS signal levels are measured with a 600-ohm termination in place of the CPE. The 600 Ohm termination is replaced by the CPE before CAS recognition or CAS talkdown testing is performed. Page 6

15 CAS Recognition Test Matrix The test matrix in Tables 2, 3, 4, and 5 may be used for CAS recognition testing. A pass condition is achieved, for a given test number, when there are zero (0) missed CAS on 1000 consecutive test attempts, at a rate not exceeding 1 test attempt every 2 seconds. The test matrix in Tables 2, 3, 4, and 5 consists of specific test conditions and may be used to define the perimeters of the multi-dimensional CAS signal space, without interfering signals, wherein the CPE shall operate when multiple impairments are present. This signal space is smaller than the space that would be defined using the extreme worst case values for each parameter. Although this matrix can be used for testing purposes, the CPE shall be able to detect CAS everywhere within the signal space enclosed by the perimeter defined in these test conditions. Table 6 contains a test for the minimum CAS amplitude for which the CPE shall not detect the CAS. Table 2 - Group 1, CAS Recognition - All Parameters at Nominal Values Test # Low Tone Hz Low Tone Level dbm High Tone Hz High Tone Level dbm Twist Level db CAS Duration ms Comments All parameters at nominal Test # Table 3 - Group 2, CAS Recognition - One parameter at a time at the extreme value Low Tone Hz Low Tone Level dbm High Tone Hz High Tone Level dbm Twist Level db CAS Duration ms Tone Frequency Limit Tests Comments Lower Tone at Low Freq Limit Lower Tone at High Freq Limit Upper Tone at Low Freq Limit Upper Tone at High Freq Limit Dynamic Range Tests Both Tones at minimum levels Both Tones at maximum levels Power Differential (Twist) Tests Negative twist Positive twist Positive twist Negative twist Signal Duration Tests Minimum CAS duration Maximum CAS duration Page 7

16 Table 4 - Group 3, CAS Recognition - Parameters at 90% from Nominal, CAS 75.5ms Test # Low Tone Hz Low Tone Level dbm High Tone Hz High Tone Level dbm Twist Level db CAS Duration ms Comments LF1= Low Tone Lower limit LF2= High Tone Lower limit UF1= Low Tone Upper limit UF2= High Tone Upper limit Both tones at 90% of nominal frequencies, low amplitude, no twist LF1, LF LF1, UF UF1, LF UF1, UF2 Both tones at 90% of nominal frequencies, high amplitude, no twist LF1, LF LF1, UF UF1, LF UF1, UF2 Both tones at 90% of nominal frequencies, low amplitude, negative Twist at 90% LF1, LF LF1, UF UF1, LF UF1, UF2 Both tones at 90% of nominal frequencies, low amplitude, positive Twist at 90% LF1, LF LF1, UF UF1, LF UF1, UF2 Both tones at 90% of nominal frequencies, high amplitude, positive Twist at 90% LF1, LF LF1, UF UF1, LF UF1, UF2 Both tones at 90% of nominal frequencies, high amplitude, negative Twist at 90% LF1, LF LF1, UF UF1, LF UF1, UF2 Page 8

17 Table 5 - Group 3, CAS Recognition - Parameters at 90% from Nominal, CAS 84.5ms Test # Low Tone Hz Low Tone Level dbm High Tone Hz High Tone Level dbm Twist Level db CAS Duration ms Comments LF1= Low Tone Lower limit LF2= High Tone Lower limit UF1= Low Tone Upper limit UF2= High Tone Upper limit Both tones at 90% of nominal frequencies, low amplitude, no twist LF1, LF LF1, UF UF1, LF UF1, UF2 Both tones at 90% of nominal frequencies, high amplitude, no twist LF1, LF LF1, UF UF1, LF UF1, UF2 Both tones at 90% of nominal frequencies, low amplitude, negative Twist at 90% LF1, LF LF1, UF UF1, LF UF1, UF2 Both tones at 90% of nominal frequencies, low amplitude, positive Twist at 90% LF1, LF LF1, UF UF1, LF UF1, UF2 Both tones at 90% of nominal frequencies, high amplitude, positive Twist at 90% LF1, LF LF1, UF UF1, LF UF1, UF2 Both tones at 90% of nominal frequencies, high amplitude, negative Twist at 90% LF1, LF LF1, UF UF1, LF UF1, UF2 Page 9

18 Test # Low Tone Hz Low Tone Level dbm Table 6 - Group 4, CAS Reject Amplitude High Tone Hz High Tone Level dbm Twist Level db CAS Duration ms Comments Both Tones below -45 dbm Talkdown Performance Parameters A CAS talkdown is defined as the failure to detect the presence of a CAS in the presence of speech, music, or noise and respond with an ACK signal within 100 ms after the end of the CAS. Three key criteria were determined to be important for measuring CAS talkdown performance. The first criterion sets a talkdown performance objective for the case of an average near-end speech level on a loop with average loss. The second criterion sets a weighted-average talkdown performance objective for the worst 1% of combinations representing loud near-end speech levels with high loss loops. The third criterion sets a global weighted-average talkdown performance objective for all combinations of near-end speech levels and loop losses. These three criteria attempt to provide an overall global talkdown performance measure tempered with the talkdown performance with average signal levels, and a measure of the worst talkdown performance that may occur. Talkdown performance measurement introduces the concept of a Modified Signal Recognition Percentage (MSRP) to account for the alternation of speakers during a typical telephone conversation. When testing talkdown performance, every CAS that is sent is theoretically accompanied by near-end speech. In reality, it is rare that the near-end talker will occupy the talk path 100% of the call time. It is more realistic to assume, as the test plan does, that on average both the near-end and far-end talkers speak approximately 50% of the call time, with few instances of double talk. The implications of such an assumption on CAS detector talkdown performance is that approximately 50% of the CAS will be received while the near-end is in the listening mode (i.e. the far-end is talking). CAS received while the near-end is in the listening mode will not be corrupted by speech and will most likely be detected if the CAS detector meets the CAS recognition recommendations in section The test plan accounts for this assumption by modifying the actual talkdown performance data to obtain what is known as the Modified Signal Recognition Percentage: MSRP = 0.5*(100% + Actual Signal Recognition Percentage(%)) The MSRP essentially provides a 50% credit in talkdown performance for all CAS detectors, assuming that the CAS recognition tests in section are all passed. In essence, the worst MSRP that a CAS detector can have is 50%. Page 10

19 CPE should meet the following criteria for talkdown performance: 1) The Modified Signal Recognition Percentage under conditions of an average CAS level (-22 dbm/tone) and an average near-end speech level (-19dBm-ASL) should be at least 99.5%. 2) The weighted-average of the Modified Signal Recognition Percentages measured under the conditions specified by the worst one percent of the 72 combinations should be at least 93%. 3) The global, weighted-average of the Modified Signal Recognition Percentages measured under the conditions specified by all 72 combinations should be at least 99.5%. (See Appendices A and B in Bellcore SR-TSV for more details.) Talkoff Performance Parameters A CAS detector talkoff is a CPE CAS detection caused by speech, music, or noise that triggers the sending of an ACK signal. Three key criteria were determined to be important for measuring CAS talkoff performance. The first criterion sets a talkoff performance objective for the case of a near-end talker with an average speech level and a far-end talker with an average speech level. The second criterion sets a weighted-average talkoff performance objective for the worst 1% of combinations representing loud near-end talkers speaking to loud far-end talkers. The third criterion sets a global, weighted-average talkoff performance objective on all combinations of near-end talkers and far-end talkers. These three measurements attempt to provide an overall global talkoff performance measure tempered with the talkoff performance with average speech levels, and the worst talkoff performance that may occur. CPE should meet the following criteria for talkoff performance: 1) Under conditions of an average near-end speech level (-19 dbm-asl) and an average far-end speech level (-28 dbm-asl), the Combined Talkoff Rate should be less than talkoffs/hour or less than 1 talkoff in 45 hours. 2) The weighted-average of the Combined Talkoff Rates for the worst one percent of the 63 combinations of near-end and far-end speech levels should be less than talkoffs/hour or less than 1 talkoff in 10 hours. 3) The global weighted-average of the Combined Talkoff Rates for all 63 combinations of near-end and far-end speech levels should be less than talkoffs/hour or less than 1 talkoff in 35 hours. (See Appendices A and B in Bellcore SR-TSV for more details.) The Combined Talkoff Rate (CTR) mentioned in the three talkoff performance objectives represents the sum of one half the talkoff rate measured for the near-end speech level plus one half the talkoff rate measured for the far-end speech level. CTR = 0.5*(near-end talkoff rate + far-end talkoff rate) The CTR is the average talkoff rate for a given pair of near-end and far-end speech levels based on the assumption that each party speaks 50% of the call time. Page 11

20 Muting Talkoff If the CPE creates a mute and does not send an ACK signal during the mute, the CPE should provide an external mechanism to detect when the mute condition starts and stops so the frequency and duration of the mutes can be measured. These types of mutes will be referred to as CAS Check Mutes. A mute condition in this case is defined to be any loss of more than 3 db inserted in the path between the transmitter to T&R, or T&R to the receiver. If a CAS Check Mute does occur, it shall be considered to be a talkoff of the CAS detector. 4.5 Adjunct Series Impedance requirements AC Impedance An adjunct device shall not contribute more than 1 db of AC loss between the frequency range of 200 to 4000 Hz, with a simulated telephone resistive AC load of 600-ohms. These conditions shall hold when the Tip & Ring DC current is between 5 and 100 ma. NOTE - The AC loss caused by the insertion of an adjunct should be as low as possible to minimize the operational impact to the connected telephone DC Impedance The voltage drop across an adjunct device shall not exceed 1 volt when the Tip & Ring DC current is between 5 and 100 ma. NOTE - The DC voltage drop caused by the insertion of an adjunct should be as low as possible to minimize the operational impact to the connected telephone. 4.6 CAS-ACK Handshake and Multiple Extension Interworking Switching systems alert CPE with a CAS prior to attempting transmission of calling line identity information for a waiting call. Multiple Extension Interworking (MEI) allows Type 2 (and 3) CPE to dynamically arbitrate responsibility for completing the CAS-ACK handshake and to synchronize line flash signaling. MEI does not require any user configuration or preprogramming. MEI uses an inter-cpe signaling method and a definitive CAS-ACK handshake timing protocol to support Off-Hook calling identity services in call scenarios where multiple CPE are simultaneously Off-Hook on the same line. MEI shall be supported by Type 2 CPE. Upon detection of CAS, Type 2 CPE shall mute the customer s Voicepath. While the voicepath is muted, no signals unrelated to the CAS-ACK handshake shall be transmitted onto Tip & Ring by the CPE. Type 2 CPE shall perform a MEI compatibility check. If no extension is in use, or all extensions are MEI compatible, one CPE shall respond to the switch with an ACK to indicate that the CPE are prepared to receive the FSK data. After the conclusion of FSK data reception, the CPE shall re-establish the voicepath. Page 12

21 4.6.1 User s Perspective MEI permits CIDCW and Call Waiting Deluxe (CWD) subscribers to receive the identity of the waiting party and exercise call disposition options when more than one MEI-capable extension is in use. MEI also allows subscribers to mix Type 2 and Type 3 CPE on the same line without adverse service interaction and preserves the plug and play aspect of Type 1,2 and 3 CPE. Because all compatible CPE monitor and receive Off-Hook data transmissions regardless of their On-Hook or Off-Hook State, MEI supports a consistent call logging feature among CPE MEI Functions MEI requires Type 2 CPE to implement three functions: 1) A CPE-based protocol that uses information about the line and CPE states to determine if a device will perform the functions of an ACK-Sender. 2) Generation and detection of DC signals to communicate between CPE. 3) A method to detect the presence of non-compatible extensions in use Line and CPE States MEI uses information about the condition of the Tip & Ring interface referred to as the Line State, and information about the hook status of the CPE known as the CPE State. The Line State can be one of two conditions: In-Use, or High. For test purposes the Line State shall be considered In-Use when the voltage on the Tip & Ring interface is 19 volts or below. For test purposes the Line State shall be considered High when the voltage on the Tip & Ring interface is above 21 volts. These voltages are used for test purposes and are based on idle line network voltages that typically range from 42 to 78 volts. CPE manufacturers however should recognize that idle line network voltages may range from 21 to 78 volts, and that CPE equipment should function correctly over this range. In some cases the idle line voltage may be less than 21 volts. Reference should be made to ANSI T1.401 and TIA/EIA 470-B. The CPE State can have one of two conditions: On-Hook or Off-Hook as defined in TIA/EIA 470-B. For the purposes of MEI, an adjunct with its attached telephone terminal is considered as one CPE Determination of the ACK-Sender The ACK-Sender is the single CPE that completes the CAS-ACK handshake and terminates the line during data transmission if no incompatible extension is detected. ACK sender status is determined on a per call basis. 1) The first CPE Off-Hook on a call shall be designated as the ACK-Sender for the entire duration of the call, even if that CPE returns On-Hook while other CPE remain Off-Hook. Page 13

22 NOTE - In some cases the designated ACK Sender may not fulfill its duty as ACK Sender (e.g. the first CPE Off-Hook is not Type 2 compliant). In these cases either the CAS-ACK handshake will not be completed (e.g. a non-compliant CPE is Off-Hook), or the Backup ACK-Sender will complete the CAS-ACK handshake if all CPE Off-Hook are Type 2 compliant when a CAS is received. 2) To determine if it is the first CPE Off-Hook, a Type 2 CPE shall detect the start of a call as a Line State change from High to In-Use, providing the Line State was High for a minimum of 1.6 seconds prior to the Line State change. Type 2 CPE shall detect the Line In-Use state no later than 500 ms after Line State changes from High to In-Use. NOTE - A line sense circuit that is responsive while in the On-Hook State will aid in reducing the occurrences of ACK-Sender glare (i.e. situations where two CPE go Off-Hook within a short period of time and both assume ACK-Sender responsibilities). 3) Type 2 CPE shall detect the end of a call when the Line State is High for 2.0 seconds or longer. The CPE may detect the end of a call when the Line State is High for 1.6 to 2.0 seconds. The CPE shall not detect the end of a call when the Line State is High for less than 1.6 seconds. 4) If the CPE is an adjunct device, it shall recognize when its attached terminal causes the line to go In-Use over the full range of Off-Hook V-I characteristics of station sets specified in ANSI/TIA/EIA-470-B. 5) If a Type 3 Assertion signal is applied to the line, the designated ACK-Sender shall relinquish its role as ACK-Sender Determination of the Backup ACK-Sender The last CPE to respond to a CAS with an ACK and successfully receive FSK data shall be designated as the Backup ACK-Sender. Backup ACK-Sender status may carry over from call to call. However, a Type 2 CPE shall give up its Backup ACK-Sender status when another CPE successfully completes the CAS-ACK Handshake and receives FSK data CAS-ACK Handshake Protocol Three key factors influence the timing of the CAS-ACK handshake protocol. First, the CAS- ACK handshake must be consistent with timing parameters expected by the network. This requires that the transmission of the ACK begin no later than 100 ms after the end of CAS as measured on the Tip & Ring interface. Second, MEI requires a check be performed to determine if non-mei CPE are Off-Hook. If such equipment is detected, the CAS-ACK handshake is aborted to prevent annoying a user with a data signal and potentially causing unreliable service. Third, the timing of the CAS-ACK handshake protocol must provide allowances for variation in CPE CAS detection delay, CAS extension by speech, CAS shortening by speech, and practical tolerances in switching the DC line termination. Page 14

23 The following rules shall govern the timing structure of the CAS-ACK handshake: 1) Each Off-Hook CPE shall proceed to the On-Hook state not earlier than 25 ms and no later than 60 ms after the end of CAS as measured on the Tip & Ring interface. NOTE - The 25 ms delay is necessary to prevent the On-Hook transition from corrupting the CAS for other CPE that may have not completely qualified the signal. The additional 35 ms that defines the 60 ms upper limit allows for variation in CAS detection delay. 2) After detecting a Line High state, the ACK-Sender shall go Off-Hook. The ACK-Sender shall allow the line to remain in the High state for at least 5 ms but not more than 8 ms. If no Line High state is detected within 100 ms after going On-Hook, all previously Off- Hook CPE shall return to the Off-Hook state. NOTE - If no Line High state is detected within 100 ms after going On-Hook, a non- MEI compatible CPE has been detected. 3) Following a CAS the Backup ACK-Sender shall monitor the line for a Line High state lasting a minimum of 15 ms and a maximum of 20 ms. Upon detecting the 15 to 20 ms Line High state, the Backup ACK-Sender shall immediately become the ACK-Sender, go Off-Hook, complete the CAS-ACK handshake, and remain as ACK-Sender for the duration of the call. 4) After going Off-Hook the ACK-Sender shall begin transmission of the ACK no earlier than 30ms and no later than 40 ms after the leading edge of the Line High voltage transition. 5) All CPE, regardless of their prior CPE State, shall be ready to receive the start of FSK data 85 ms to 605 ms after the leading edge of the Line High voltage transition. NOTE - The 85ms duration is composed of 30 ms minimum ACK delay plus 55 ms minimum DTMF ACK length. The 605ms duration is composed of 40 ms maximum ACK delay, plus 65 ms maximum DTMF ACK duration, plus 500 ms maximum FSK delay. 6) All CPE shall return to their previous state and be ready to receive CAS (On-Hook or Off-Hook) within 50 ms after the end of reception of data. 7) If data transmission does not begin within 605 ms from the start of the Line High pulse all CPE shall return to their previous state and be ready to receive CAS within 50 ms. 8) All CPE shall monitor the line while On-Hook or Off-Hook to receive Caller-ID messages to maintain a consistent call log. Page 15

24 Mute the talking and listening paths. No signals unrelated to the CAS-ACK handshake shall be transmitted. < 100ms All CPE return to their previous state and Reestablish the talking and listening paths < 50 ms CAS ACK FSK Data 25ms - 60ms *1 30ms - 40ms 5ms - 8ms 85ms - 605ms *2 SCENARIO-1: ACK-Sender returns ACK ACK-Sender returns Off-Hook and begins transmission of the ACK signal. Line State SCENARIO-2: ACK-Sender does not go back Off-Hook and Backup ACK-Sender assumes role 15ms - 20ms Backup ACK-Sender returns Off- Hook and begins transmission of the ACK signal. Line State *1. It is desirable to have the Line High signal begin as soon as possible in this period *2. If no data is received within 605ms then all CPE shall return to their previous state within 50 Figure 1 - CAS-ACK Handshake Diagram As indicated in Figure 1, the CAS-ACK handshake protocol allows for up to 35 ms of CAS detection delay and signal extension after the true end of CAS. It also allows for up to 25 ms of signal shortening. The ACK delay has taken into account practical tolerances on switching the DC line termination ACK Signal Generation The ACK signal is a dual tone signal, commonly referred to as DTMF D. The network requires that the CPE begins to transmit the ACK signal within 100ms after the end of CAS transmission. Refer to Bellcore GR-30-CORE. NOTE If the switch does not receive the ACK signal within the required time limits, a time out occurs, the DTMF receiver is disconnected, and the far-end is reconnected. All DTMF transmission characteristics shall meet the requirements of ANSI/TIA/EIA-470-B. Page 16

25 4.6.8 Voicepath Mute Control CPE shall mute the customer s Listening and Talking Paths and disable the DTMF keypad no earlier than 25 ms and no later than 60 ms after the end of CAS as measured on the Tip & Ring interface. CPE shall provide at least 50 db of attenuation between the line and both the customer s Talking and Listening Paths across the frequency band of 200 to 3200 Hz. CPE shall restore the Voicepath within 50 ms after the end of the FSK signal. The CPE shall interpret the end of the FSK signal as any of the following: 1) Absence of carrier signals on the line between Hz. Signals below 0.3 mv rms shall be interpreted as absence of carrier. Signals between 12mV rms and 0.3 mv rms may be interpreted as absence of carrier. 2) More than 5 framing errors in the FSK message. 3) More than 150 ms of continuous mark or Space signal at 12 mv rms or higher. The CPE shall stay in the muted state regardless of the data bytes decoded until one of the conditions stated above are met (i.e. the CPE shall not simply unmute after the checksum). NOTES - 1) This functionality should allow the CPE to stay muted during an actual FSK transmission (i.e. for caller-id or an ADSI message), but the CPE will not stay muted if the FSK carrier detected is due to speech or noise. 1) It is desired that the mute duration following the FSK be as short as possible for systems using a secondary transmission system from the FSK demodulator to a remote device (e.g. a cordless phone) Inter-CPE Signaling The ability to arbitrate ACK-Sender responsibility and to request a synchronized Flash is provided by an inter-cpe signaling method that modulates the DC line voltage with a pulse signature pattern Request to Flash Signaling MEI provides the capability for multiple Off-Hook CPE to synchronize line Flash signaling for the purposes of feature activation and control. In order to accomplish a synchronized Flash, all Off-Hook CPE need to simultaneously proceed On-Hook for a specified period of time. An RTF signal has been defined to initiate a synchronized Flash for all Off-Hook CPE. Type 2 CPE shall be able to generate an RTF signal whenever Flash signal generation is required. Type 2 CPE shall be able to detect and respond to an RTF signal generated by another Off- Hook MEI compatible CPE. Page 17

26 Request to Flash Signal Generation Type 2 CPE shall be able to generate an RTF signal with the timing pattern of T1 = 140 ± 10 ms On-Hook, T2 = 440 ± 10 ms Off-Hook, and T3 = 600 ± 10 ms On-Hook, then return to Off-Hook. The synchronized Flash signal will be generated during the T3 interval. T1 T2 T3 On-Hook Off-Hook Figure 2 - CPE state generating RTF, multiple CPE Off-Hook, successful synchronized Flash T1 T2 T3 Line High DC level shift with Line In Use Figure 3 - Line state during RTF, multiple CPE Off-Hook, successful synchronized Flash If a Line High state occurs during T1 of the RTF signal, the CPE generating the RTF shall extend the pulse width to that of a Flash signal. NOTE - This capability allows a CPE to generate a Flash without the RTF signal if that CPE is the only CPE Off-Hook. T1 = Flash Line High Line In Use Figure 4 - Line state during RTF, single CPE Off-Hook Page 18

27 If a Line High state does not exist within 140 ms after the start of T3 the CPE generating the RTF shall abandon the synchronized Flash attempt and return to the Off-Hook state within 175 ms after the start of T3. T1 T2 T3 On-Hook Off-Hook Figure 5 - CPE state generating RTF, multiple CPE Off-Hook, unsuccessful RTF T1 T2 T3 DC level shift with Line In Use Figure 6 - Line state during RTF, multiple CPE Off-Hook, unsuccessful RTF Request to Flash Signal Detection and Response Type 2 CPE shall be able to detect the RTF signal generated by another MEI-compliant CPE if the DC voltage change is 500 mv, or 5% of the Line In-Use voltage prior to the RTF, whichever is greater. Off-Hook Type 2 CPE shall go On-Hook within 100 ms of the start of T3 to produce a synchronized Flash, then return Off-Hook 1250 ± 50 ms after the start of T3. NOTE CPE responding to an RTF remain On-Hook after the start of T3 longer than the CPE initiating the synchronized Flash to allow CPE supporting CWD to signal their DTMF option without interference. T1 T2 T3 On-Hook Off-Hook Figure 7 - CPE state detecting and responding to an RTF, successful synchronized Flash Page 19

28 T1 T2 T3 Line High Line In Use Figure 8 - Line state during RTF, Multiple CPE Off-hook, successful synchronized Flash If a Line High state does not exist within 140 ms after the start of T3 the CPE responding to the RTF shall abandon the synchronized Flash attempt and return to the Off-Hook state within 175 ms after the start of T3. T1 T2 T3 DC level shift with Line In Use Figure 9 - CPE state detecting & responding to an RTF, unsuccessful RTF T1 T2 T3 DC level shift with Line In Use Figure 10 - Line state during RTF, multiple CPE Off-Hook, unsuccessful RTF Type 3 Assertion Signaling MEI provides the capability for Type 3 CPE to take over the role of ACK-Sender Type 3 Assertion Signal Characteristics A Type 3 Assertion Signal is assumed to be generated with a timing pattern of T1 = 310 ± 10 ms On-Hook, T2 = 140 ± 10 ms Off-Hook, and T3 = 310 ± 10 ms On-Hook, then return to Off-Hook. It is assumed that a Type 3 Assertion Signal will not be applied within the first 500 ms after a Type 3 CPE is taken Off-Hook. Type 2 CPE shall not generate Type 3 Assertion Signals. Page 20