MAINTAINING OPTIMAL ALARM MONITORING COMMUNICATION 2. MULTIUSER RF, DSSS AND PUBLIC NETWORKS Optimal communication from outstations to the control room is crucial to provide a reliable monitoring service. This document covers the various types of shared or public network communication systems and steps that can be taken to maintain good communication and how to resolve common interruptions to the outstation monitoring equipment at the control room. It is important to note any new equipment installations, upgrades, repairs or maintenance that is done in the control room, as it is usually after these events that communication interruptions occur. VHF MULTI USER NETWORK SYSTEMS VHF monitoring systems utilise a base station with an LCD screen, receiver control buttons/knobs that are connected to the Control Room computer and monitoring software. The following steps will help to locate and resolve common problems found in the control room environment. 1. Outstation signal loss No signals are received or a specific area s signals are not being received. Here are some system checks that can be done: Locate the base station and check if the display and power indicator is on. On the base display, check for any system failure or fault indications that may be present. Look at the control room monitoring software for repeater, low battery or communication failure event reports. Repeater test failure will be a direct indication of a specified area that is no longer in communication. Inspect the antenna connection and make sure it is properly screwed on. Open the squelch and turn up the volume on the base and confirm that a the receiver mush is audible without external interference. Visually inspect the external antenna to confirm it is intact and in the correct vertical position. Make sure that your monitoring software and system user licences are up to date as this will also limit or disconnect your services. Perform a localised and external customer test to confirm that the system is corrected or if the problem still exists. Replace the Base station with the spare unit and perform a local and external outstation test. If all the checks above have been done without resolve, contact the equipment manufacturer for further assistance. 1. 1
2. Signal Jamming Signal jamming or interference could be accidental or deliberate. Accidental jamming is caused by older crystal controlled transmitters with a single action TX key switch that when damaged could cause the transmitter to continuously transmit limiting the signals received at the control room. A deliberate interference signal could be created by a person with RF background utilising a company s transmitter to affect the monitoring company signal reception. Localized signal interference in the control room can also occur from adjacent equipment like printers, PABX systems, wifi modems and GPRS base stations. Jamming Detection Signal interference can be detected on the base receiver. Set the receiver squelch open and listen for an interfering signal. Without interference the receiver mush is a clear hissing sound. Remedy Check if any new equipment has been installed or upgraded in the control room that could affect the reception. If so temporarily shut the equipment down and monitor the receiver squelch to determine if the interfering signal is still present. For localised interference the interfering equipment and cable can be positioned as far as possible from the base station and on a different vertical plane. PABX phone lines must be moved away from the RF antenna cables and base station position. Call the network provider so that a qualified RF technician can assist you with solving any localised interference problems. If there is any exterior RF interference, contact the network provider to track the interference signal. 3. Equipment Installation The base station should be fitted in a secure cabinet or within a control room console. All cabling for antenna, communication and power must be securely anchored or inside cable trunking. Antenna systems must be installed on the exterior of the control room on a mast. AC power must be connected to the control room UPS supply. Base stations must have a battery backup supply that is connected. 4. Equipment maintenance Inspect the base antenna cables for damage and ensure that connectors are secure. Inspect cable anchors and power/communication connectors to the equipment for damage. 1. 2
Visually inspect the external antennas and ensure they are still in place and intact. Inspect the antenna and cable on the exterior mast and ensure that the cable is securely cable tied. When additional equipment has been installed at the control room, always verify the system operation in case the new equipment has adversely affected the base receiver signal or sensitivity. The backup battery current capacity must be checked every 6 months and batteries should be replaced every 18 to 24 months where standard lead acid batteries are used. A backup base must be started up and tested on a regular basis and the batteries checked. DSSS DIRECT SEQUENCE SPREAD SPECTRUM DSSS monitoring system utilise a PTSN, diginet, ADSL, GSM data modem or RF link connected to a Control Room computer and monitoring software. The following steps will help to locate and resolve common problems found in the control room environment. 1. Outstation signal loss No signals are received on the monitoring software. Locate the RF base (if installed) or modem and check if the display and power indicator is on. If RF, inspect the antenna connections and make sure they are properly screwed on. Ensure that the PTSN connections to the modem are secure. Inspect the ADSL, DIGINET or GSM communication cables to the computer and ensure that they are securely connected. Where GSM modems are used, look at the display and check the signal strength and network connection status icon to confirm good network connection. Look at the control room monitoring software for network or communication failure event reports. Make sure that your monitoring software and system user licences are up to date as this will also limit or disconnect your services. If all the checks above have been done without resolve, contact the equipment manufacturer for further assistance. 2. Signal Jamming The very nature of the design of the DSSS network is to overcome signal jamming. This communication system is only provided by a single service provider in South Africa and to date there have been no recorded cases of signal jamming. 1. 3
3. Equipment maintenance The GSM, ADSL or diginet modems should be fitted in a secure cabinet or within a control room console. All cabling, communication and power must be securely anchored or inside cable trunking. Network and PTSN cabling must be labled. GSM gain antenna systems must be installed on the exterior antenna mast. GSM modems with internal antenna systems should not be installed within metal equipment racks. Modem power supplies must be connected to the control room UPS supply. RF Base stations must have a battery backup supply that is connected. Preferably two separate communication modem connections should be available as a failover if network interruptions occur. GSM/GPRS GSM /GPRS monitoring systems use a base station with an LCD screen or just a modem that connects to the Control Room computer and monitoring software. The following steps will help to locate and resolve common problems found in the control room environment. 1. Outstation signal loss No signals are received at the base or on the monitoring software. Locate the base station / modem and check if the display and power indicator is on. Visually inspect the antenna connections and make sure they are properly screwed on. Look at the display and check the signal strength and network connection status icon. Look at the control room monitoring software for network, low battery or communication failure event reports. Make sure that your monitoring software and system user licences are up to date as this will also limit or disconnect your services. If signals are constantly received after a long delay, there may be a network overload and a different network may have to be used in your area. If all the checks above have been done without resolve, contact the equipment manufacturer for further assistance. 2. Signal Jamming Signal jamming as in VHF can be induced by criminals using a jamming device that constantly transmits on all GSM frequency bands, resulting in the GSM device not being able to register or communicate effectively with the GSM network. It is important to first do basic equipment and antenna cable tests before assumptions of signal jamming are made, as it will save time in identifying and rectifying signal loss conditions. 1. 4
Detection Signal Jamming can be detected by a complete loss of signal and network connection. It is important not to confuse a base station constantly switching between two serving network cells causing signal fluctuations as signal jamming. Signal stability must be constantly maintained without a large variance at any time of day. Confirm signal jamming by looking at cell phone handset signal reception. Remedy Notify the network provider and equipment manufacturer of the jamming. Jamming devices have to be in close proximity to the area being jammed (within 30 to 50 meters), so unauthorised people and vehicles near the control room must be investigated. Jamming equipment is usually a box with 2 to 14 GSM antennas mounted on it. 3. Equipment Installation The GSM/GPRS base station should be fitted in a secure cabinet or within a control room console. All cabling antenna, communication and power must be securely anchored or inside cable trunking. Antenna systems must be installed on the exterior antenna mast. AC power must be connected to the control room UPS supply. Base stations must have a battery backup supply that is connected. When the base is located in a densely populated hi rise building environment it is essential to use directional antennas and dual receiving Network providers. This is to make sure the GSM base is logged into a preferred tower and does not randomly switch between all the additional available towers installed to cope with hi volume of GSM subscribers. Preferably two separate network connections should be available for network signal interruptions and general overloading of data connections at the same time. 4. Equipment maintenance Inspect antenna cables for damage and ensure that connectors are secure. Inspect cable anchors and power/communication connectors to the equipment for damage. Verify that the GSM signal strength is still at its optimum level at the control room. If two GSM providers are used on site for redundancy purposes, force the unit to switch to the back-up provider and test signal strength and GSM functionality. When additional equipment has been installed at the control room, always verify network signal strength in case the new equipment has adversely 1. 5
affected the GSM base operation. Visually inspect the external antennas and ensure they are still in place and intact. Inspect the antenna cable on the mast and ensure that they are securely cable tied. Backup batteries must be checked every 6 months and replaced every 18 to 24 months where lead acid batteries are used. PTSN-(PUBLIC SWITCHED TELEPHONE NETWORK) PTSN monitoring systems utilise a Base Station with single or multiple telephone line inputs to receive alarm panels activations and status events. Telkom is the sole provider 1. Outstation signal loss Locate the base station and check if the display and power indicator is on. Look for a visual or computer communication indicating a physical phone line failure. Inspect the phone line connectors to the base and ensure that they are securely connected. Make sure that your monitoring software user licence is up to date as this will also limit or disconnect your services. Make sure that TELKOM has not disconnected your services. If all the above options has been tested, contact the equipment manufacturer for assistance. 2. Physical line signal interruption and interference. Phone line interruptions are usually caused by lightning damage, water or cable theft. Where cable theft has occurred it is usually not repaired very quickly and the system will be disconnected during this period of time. Where an interchange is damaged it is usually repaired the same day if the damage is not that severe. 3. Equipment installation The PTSN base station should be fitted in a secure cabinet or within a control room console. All cabling phone, communication and power must be securely anchored or inside cable trunking. Incoming phone lines should be labelled. Phone line cabling must not be next to or in the same trunking as AC power cables. AC power must be connected to the control room UPS supply. Base stations must have a battery backup supply that is connected. 1. 6
4. Equipment maintenance Inspect cable anchors, phone line, power and communication connectors to the equipment for damage. Backup batteries must be checked every 6 months and replaced every 18 to 24 months. Base stations should be well earthed for the phone line lightning protection to be effective. The backup base station must be powered up periodically to test its operation. 1. 7