SERVICE 1 A2 KEY TELEPHONE SYSTEM KEY SERVICE UNITS 550- AND 551-TYPE

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1 BELL SYSEM PRACCES A & Co Standard SECON ssue, uly 976 SERVCE A2 KEY ELEPHONE SYSEM KEY SERVCE UNS 550 AND 55YPE. GENERAL.0 his section provides identification, installation, connection, and maintenance information for the 550 and 55type KSUs. he information pertaining to the 550A, 55A, 550B, and 55B KSUs was formerly contained in Sections and hese units have been rated MD and replaced by the 550C and 55C KSUs, which are covered for the first time in this section. nformation required for maintenance of existing installations of the MDrated KSUs has been retained in this section..02 Whenever this section is reissued, the reason for the reissue will be listed in this paragraph. 45A (Automatic, DC Signaling ie Line Circuit) 467A (LowVoltage Monitor Circuit) Application A2 KS installations Ordering Guide (a) Basic Units (Fig. ): Unit, Service, Key550C (for installations where suitable external source of required talk and signal voltages is available).03 his issue of the section is based on the following drawings: Unit, Service, Key55C (builtin power unit). SD694770, ssue SA (b) Replaceable Components: CD694770, ssue 4B f this section is to be used with equipment or apparatus reflecting later issues of the drawings, reference should be made to the SD and the CD to determine the extent of the changes and the manner in which the section may be affected. 2. DENFCAON nterrupter, KS975, List furnished with 550 and 55type KSU (requires 0V ac motor supply) Unit, Power, 86738A, List (MD)furnished with 55A KSU (MD) Unit, Power, 28Afurnished with 55B KSU (MD) 2.0 Purpose: A 550 or 55type KSU provides a factorywired A2 KS package arranged to mount four of the following KUs: Unit, Power, 28Dfurnished with 55C KSU Lamp, 5A 400type (CO or PBX Line Circuit) 40A (Manual ntercom Line Circuit) Fuses, Bussman, MDL ( ampere, one per power unit) NOCE Not for use or disclosure outside the Bell System except under written agreement Printed in U.S.A. Page SP S825407i l.jpg Scanned by Frank Harrell, (Cowbo Frank) Castle Rock, Colorado Oct 4,202 6:38:7

2 SECON POWER UN CONNECOR NOE: 550C KEY SERVCE UN S SAME AS 55C EXCEP DOES NO HAVE POWER UN. Generator, Frequency ll8afor use with 550B, 550C, 55B, and 55C KSUs; 05V ac ringing supply (supplied with three mounting screws) Bracket, Mounting, for mounting ll8a frequency generator on 550/55C KSU Kit of Parts, D80699for mounting ll8a frequency generator on 550/55B KSU. (d) Associat ed Apparatus (order separately): CONNECNG BLOCK Cord, Power, (P4 W765), /2 feet* Cord, Power, (P40326), /2 feett Cord, Power, (P4 W766), 2 feet* Cord, Power, (P40327), 2 feett Cord, Power, (P4 W767), 4 feet* Cord, Power, (P40328), 4 feett Cord, Power, (P4 W768), 6 feet* Cord, Power, (P40329), 6 feett Cord, Power, (P40099), 2 feett CABLE CLAMP 8 A FREQUENCY FOR EXERNAL GENERAOR AC POWER CORD Fig. 55C KSU With Frequency Generator Plate, Adapter, ll (P48F26) *For 55A KSU (MD). tfor 55B KSU (MD) or 55C. For mounting two single width or one double width A Key elephone System angle bracket type KUs in 550type KSU. Fuses, 24E (/2 ampere, three per power unit) Fuses, 24B (3 ampere, one per power unit). (c) Replaceable (O ptio nal) Compo nents: Order required combination of up to four of the following KUs, subject to specified limitations: Unit, elephone, Key, 400D (maximum of four) nterrupter, KS9385, List (MD) (requires 24V de motor supply) Unit, elephone, Key, 40A (maximum of four) nterrupter, KS9385, List 2 (requires 24V de motor supply) Unit, elephone, Key, 45A (maximum of three) Page 2 BSP i0_ jpg Scanned by Frank Harrell, (Cowboy Frank) Castle Rock, Colorado Oct 4, 202 6:39:

3 SS, SECON Unit, elephone, Key, 467A (maximum of one) 2.04 Design Features Common audible signaling can be provided by appropriate strapping on the connecting block. 550type KSUs do not have internal power units, while 55 types are factoryequipped with plugin power units: 55C28Dl Power Unit 55B (MD)28A Power Unit 55A (MD)86738A, List Power Unit (MD) he basic KSU assembly contains four jacks for 400series KUs, two separate jacks for a plugin KS interrupter and a plugin power unit, and a factorywired connecting block with "quickclip" terminals. 3. NSAUAON AND CONNECONS 3.0 he information in 3.02 through 3.7 applies specifically to the 550C and 55C KSUs, and also to the 550A, 55A, 550B, and 55B KSUs (all MD), unless otherwise noted. Most new installations will involve the "C" KSUs, but the MD units will be encountered in existing installations. For methods of strapping and terminating wire and cable, refer to Section Cables and wire must be brought into the 550C and 55C KSUs from the bottom. Clamps are provided for retaining the power, line, and station cables. Dress wires along the sides of the connecting block. n the "A" and "B" KSUs, cable and wire may enter from top or bottom. All external connections are made on front of connecting block. NSALLAON he 0volt ac operated KS975, List interrupter furnished with each KSU provides lamp flash, wink, and audible signal feature interruptions. t is a plugin unit locked into place by a captive screw. A 24volt de operated KS9385, List (MD) or List 2 interrupter can be substituted for the one furnished with the KSU at locations where only 24volt de power is available. ntended for vertical mounting on a wall or other suitable surface Mounting: Mount the KSU on a clean, firm, dry, vertical surface where it is easily accessible for service (mounting hardware to be obtained locally depending on mounting surface). f the KSU has a builtin power unit or if it is to be equipped with a 8A frequency generator, it must be located within cord length of a grounded 7V 60Hz power outlet provided by the customer (see Ordering Guide for cord lengths). he outlet should be separately fused and not under the control of a switch. A KSU without builtin power unit should be mounted as close as possible to the separate telephone company power source. Protective front and back covers provided. 550C and 55C have line status lamps which display the same signals as the line lamps at associated stations. 550C and 55C are 7.8 inches high, 9.7 inches wide, and 7.2 inches deep.. 550B/55B (MD) and 550C/55C can be equipped with a 8A frequency generator which provides power for operating ringers at associated stations. Earlier type KSUs must be connected to an external ringing supply. Warning: Do not connect the KSU to external power until all other wiring is complete and all KUs are installed External AC Power Cord: An external ac power cord is required with all 55type KSUs and with any KSU equipped with a frequency generator. (a) KSUs: Open the cable clamp in the lower left corner of the KSU and insert the receptacle end of the external power cord into the trough; secure the cord with the clamp. Page 3 BSP i0_ jpg Scanned by Frank Harrell, (Cowboy Frank) Castle Rock, Colorado Oct 4, 202 6:39:3

4 SECON (b) 55B KSU (MD) Only: he 55B KSU is shipped with its power unit cord carried through an insulating grommet in the bottom of the KSU case. o install an external power cord: () Compress the grommet to release it from the case. the kit. Mount the bracket on the door of the KSU as shown in Fig. 2. Attach the frequency generator to the bracket with the three screws supplied with the generator. Connect the feedthrough type plug to the external ac power cord and, if the KSU is a 55B, to the power unit cord (see 3.03b] for instructions on positioning the grommet). (2) Remove the grommet from the internal power cord. (3) nsert the receptacle end of the external power cord through the cutout in the housing where the grommet was removed. (4) Place the grommet around the external power cord. (5) Seat the grommet in the cutout, again from inside the case. (6) Connect the external power cord to the power unit cord. CONNECONS 3.05 able A provides a key to the connection diagrams in this section for the various models of the 550/55 KSUs nternal Power: he 55type KSUs have builtin, factorywired power units, and normally require no internal power wiring by the installer unless 05volt ac ringing voltage is required (see 3.07 for details). KSUs of the 550type must be wired to a suitable external power supply for all operating voltages. Make all external power lead connections to the terminals in the D or E columns on the front of the connecting block. nspect existing installations of 55B KSUs for improper installation of grommets and power cords (ie, grommet around power unit cord). where necessary. Correct (c) 55A KSU (MD): Connect the external power cord to the power unit cord through the cutout in the bottom of the KSU case Frequency Generator: nstall the 8A frequency generator on the 550/55C KSU as described in (a) or on the 550/55B as described in (b). Connect as described in (a) Attach the generator to the mounting bracket (Fig. ). ( ) with the three screws supplied hen snap the pins of the bracket arms into the holes in the backboard flanges of the KSU. Let the generator rest against the front of the interrupter with its power cord to the left. Connect the feedthrough type plug to the external ac power cord and, if the KSU is a 55C, to the power unit cord. (b) o mount a 8A frequency generator on a 550/55B KSU, first install kit of parts D Remove the cable clamp provided with the KSU and replace it with the one in f an external power source is to be used, be sure that it can supply the minimum 20 volts de signal battery required by 400series KUs. f it cannot, convert the KSU to a 55type by installing an appropriate power unit (see Ordering Guide) Audible Signaling Voltage: Audible signaling can be provided at the stations associated with the KSU on either the ringer or the buzzer at each telephone set. Ringer voltage must be supplied from a separate 05volt ac source, such as the 8A frequency generator, connected to the RG and RB terminals on the front of the connecting block. Buzzer voltage can be derived from the 8volt ac audible signal supply available at the internal or external power unit. Connect buzzer voltage by installing straps from terminals G± and S± to RG and RB, respectively Common Audible: his feature allows multiple stations to receive incoming call signals from the same line and a single station to receive signaling from several lines. Common audible signaling is provided by strapping together the appropriate R leads at the connecting block and wiring signaling voltage to the RG and RB terminals. Auxiliary control of common audible Page 4 BSP i0_ jpg Scanned by Frank Harrell, (Cowboy Frank) Castle Rock, Colorado Oct 4, 202 6:39:49

5 SS, SECON BRACKE NCLUDED N D80699 K OF PARS BA FREQUENCY GENERAOR Fig (MD) KSU With 8A Frequency Generator nstalled signaling is possible through the use of a separately mounted 227type KU wired to the connecting block Line Connections: Connect the incoming CO/PBX lines to the R terminals (43 to 50) in the A column of the connecting block. he KSU can accommodate a maximum of four lines. 3.0 Station Connections: erminate the station cables on the connecting block, the first cable on column A, the second on column B, Page 5 BSP i0_ jpg Scanned by Frank Harrell, (Cowboy Frank) Castle Rock, Colorado Oct 4, 202 6:40:5

6 SECON ABLE A CONNECON DAGRAM NDEX 550/55C 550/55B(MD) 550/55A(MD) erminal Layout with Station and Fig. 3 Line Connections Power Connections Fig. 5 Fig. 4 Fig. 4 Fig. 6 Fig. 7 Common Audible Connections Fig. 8 Fig. 0 Fig. 0 Common Audible Auxiliary Control Fig. 9 Connections Fig.ll Fig.ll Manual ntercom Connections See 3. See 3.3 See 3.3 Lead Designations Fig. 2 Fig. 2 Fig. 2 etc. A maximum of five stations can be wired directly to the KSU. f more stations are required, use loopthrough terminations or provide distribution facilities. Connect the ringer or buzzer leads of the station cables to the BR terminals. 4 for the manual intercom KU, disconnect the BRW/WBR pair from the back of the connecting block, and connect the pair from the other jack as shown in able B. nsulate and store the disconnected pair. Manual ntercom Grounding 3. his feature is provided by installing a 40A KU in the KSU. n early production models of the 550/55C KSUs, only jack 4 was factorywired with the talk (A) battery and ground required for operation of the 40A. Later models (indicated by an asterisk *] stamped after the code on the KSU) are wired to accept a 40A KU in any of the four jacks. 3.2 he early models can be modified to accept a 40A in another jack by disconnecting the green wires from terminals 3 (A grd) and 8 (A bat) of 4 on the back of the KSU, and transferring them to the same terminals of the desired jack. 3.3 On the 550/55A and B KSUs (MD), the talk battery terminals are factorywired at each KU jack, but only the BRW/WBR pair on 4 is wired back to the talk battery terminals on the connecting block. he pairs from the other jacks are dead dressed. o use a jack other than 3.4 Any installation of the 550/55type KSU should be grounded and protected in accordance with the requirements in Section he frame of the KSU power unit is grounded through the third, or "green," wire of its power cord. he local or circuit ground of the power unit, which is the positive side of the de output, should be connected to the same ground as the system protector. Do not connect circuit ground and frame ground together. 3.5 he 550/55C KSU has an external grounding terminal, labeled LOC GRD, on the front of the backboard above the interrupter. t is wired internally to the power unit ground circuit at the G± terminal of the connecting block. Connect this terminal to protector ground with a 4gauge wire brought through one of the cable clamps below the connecting block. On 550/55A and B KSUs (MD), a multiplepost grounding terminal is located on the top of the connecting block. Page 6 BSP i0_ jpg Scanned by Frank Harrell, (Cowboy Frank) Castle Rock, Colorado Oct 4, 202 6:40:38

7 SS, SECON S ABLE B MANUAL NERCOM WRNG 550/55A AND B (MD) KSUs CONNEC ALK BAERY PAR O CONN BLOCK ALK BAERY PAR /55B A (F43} BA (F44) WBL BLW W0 WG WBR 0W GW BRW 550/55A A (F45) BA (F46) WBL BLW W0 WG WBR 0W GW BRW * Factorywired. 3.6 Connecting of KUs: nsert each KU Note: Be careful when inserting or removing into its receptacle with a gentle, vertical plugin type KUs to avoid damage to the rocking motion until it is firmly seated. hen printed wiring and other circuit components. lower the locking bar to hold the KU in place. Blister packs should be used when returning KUs. Do not drive more than 20 line lamps from one 400type KU or more than 50 lamps from one interrupter contact nterrupter Replacement: When replacing the KS975 0volt interrupter with a KS volt type, either at initial installation 3.7 External Power Connections: After all or as a repair procedure, it is necessary to change internal connections have been made, the the connecting block wiring (see Fig. 5, 6, and 7). KSU properly grounded, and the KUs installed, Remove the strap which supplies 0V ac to the connect the KSU to the required external power motor lead (Fig. 5}, and connect whatever wiring source. is required to supply 24V de from internal or external supplies. he interrupter is removed by 4. MANENANCE loosening the captive screw in the right center of the unit, and pulling it out of the plug. 4.0 Maintenance activity on the 550/55type KSUs should be limited to the following: 4.03 WireWrap Connections: he KS6492, Clearing wiring troubles List 2 unwrapping tool should be used when removing solderless wrapped connections on line Fuse replacement jack contacts, if required, for circuit testing. he 635B tool may be used to reterminate a wire on a Lamp replacement wrapping terminal, but wires must be soldered when reconnected to ensure circuit reliability. Replacement of defective KUs, power units, interrupters, and frequency generators. Page 7 BSP i0_ jpg Scanned by Frank Harrell, (Cowboy Frank) Castle Rock, Colorado Oct 4, 202 6:4:00

8 SECON LNE LNE 2 O KEY ELEPHONE SES LNE l LNE 4 VACAN O CO OR PBX Ll NES (NOE 4) c A () R (2) A A (l) (4) (5) L (6) R (7) (B) A (9) A (0) () L (2) () R (4) A (5) A (6) (A) (B) (C) (7) 0 <><> L (B) (9) R (20) A (2) A (22) (2l) L (24) (25) (26) Bl (27) <><> (28) <><> 8 (29) <><> (O) <><> AUO BLE Bl (l) <><> SGNAL (l2) <><> CONNECONS Bl (ll) VACAN (NOE 4) c ''"" Ll NE 2 LNE l LNE 4 c c c (l4) <><> CA (l5) <><> CA (6) <><> CA (l7) CA (l8) <><> (l9) (40) <><> 0 (4) 0 (42) <><> 0 R (4l) (44) <><> (45) R (46) <><> (47) <><> R (48) o<> R (49) o<> (50) (D) (E) B R A A L R A A L R A A 0 0 L 0 0 <><> <><> <><> <><> R A A 0 0 "' 0 0 ttl <><> 0 0 LB 0 0 G± L S± GA <><> 8A 0 0 GB G8 <><> BB <><> BB 0 0 RG RB NOES,. NUit!ERS At{) LEffiRS N PARENHESES ARE FOR REFERENCE ONLY At{) DO NO APPEAR ON BLOCK 2. LEAD DESGNAONS ARE MOLDED NO FANNNG SRPS l. ALL CONNECONS O KU ACKS, BULN PO.'R UN, 00 NERRUPER ARE FACORY W REO ON REAR OF CONNECNG BLOCK 4. VACAN ERMNALS MAY BE USED FOR BUON At{) BUZZER SGNALNG CRCUS, EC., AS REQURED ) MOOR SAR FOR 24V DC OPERAON ) MOOR SAR FOR 0V! OPERAON }=cr' ) O 8A FREQUENCY GENERAOR FOR NG NG VOLAGE FRON VEW Fig. 3erminal Layout of Connecting Block on 550/55C KSU Showing nstaller Connections for ncoming Lines and Stations Page 8 BSP i0_ jpg Scanned by Frank Harrell, (Cowboy Frank) Castle Rock, Colorado Oct 4, 202 6:4:8

9 SS, SECON OESG SRP DESG SRP () ''"" A 2) ooo oo<> (3) 00 oo<> (4) (5 ooo """ l A (6) ooo (7 ooo (8) <><>o0 (9) <><>o0 O KEY ELEPHONE SES """ l A {0) oo<> (} oo<> (2) ooo {3) (4 ooo (5} ooo FACORY WRNG FROM CLP F O ACK 4 (6) ooo (7) ooo (8) <><>0<> LNE 4 A VACAN t ( (9) ooo (20 ooo (2 ooo 22) (23) ooo (27 (24 ooo (2!5) ooo (26) ooo M FOR 24V DC OPERAED KS9385, L tmo OR KS9385,LZ NERRUPER {SEE FG. 7) VACAN ERMNALS MAY' BE USED FOR BUON AND BUZZER SGNALNG CRCUS EC. AS REQURED. 8 (27) (28) ooo oo<l 2 a AUDBLE SGNAL CONNECONS "" " LNE ( LNE 2 ( O CO OR PBX LNES LNE 3 ( LNE 4 ( CA CA CA CA (29) ooo ooo (29) (30) <><><> ooo t 30 (3) ooo 3 (32 o<>0 32 ooo ( 33) (36) <><><> (36 (37 <><><> (37) (38) <><><> (38 (39) (33 (34) (35} <><><> (35,': : :=:=: (4 4) ooo (44) ( 4 ooo (40) (4) 42 ooo (42) ( 4 3 ) ooo (43) (45) (46) (47) (48) (49) (50) MG M8 L8 G± S< GA 8A G8 G RG R8 O VACAN t MOOR SAR FOR 24V DC OPERAON MOOR SAR FOR OV"! OPERAON POWER CONNECONS ERMNAE HERE (SEE FG. 6) POWER (35) (36 (37) (38) {39) (40) (4 ) (42) (43) (44) {45) (46) (47) (48) (49) (50) M L8 G " GA 8A G8 88 RG RB MOOR VACAN t SAR * POWER CONNECONS ERMNAE HERE (SEE fig 7) ERMNAE NCOMNG SERVCE ON ERMNAL B. FOR 5506 AND 556 KSU FOR 550A (MD) AND 55 A (MD) KSU Fig. 4 erminal layout of Connecting Block on 550/55A and B (MD) KSU Showing nstaller Connections for ncoming lines and Stations Page 9 BSP i0_ jpg Scanned by Frank Harrell, (Cowboy Frank) Castle Rock.,.;;, Co ;;:l.;;, o;.:ra:;; d: ;: o...;; O :;; c.:. t.:,4;:,, 2;.;; 0;.;: :;: 2 :.;6 :.; : ;;. 4 :.; : ;.; 4 ;;. 9

10 SECON O 24V OC FOR NERRUPER (NOE 2) O LA"" A' NERRUPER O AUDBLE SG O ALK BA FOR MANUAL NERCOM MG 0V± G BV± A GRD A BA PROVDE SRAPS ""EN 05 Vt RNGNG S NO USEO O 2026V OC SG BA O BA RG FREQUENCY GENERAOR FOR NG NG VOLAGE B GRD B BA 05V± :.. ' PAR OF CONNECNG BLOCK ' ; <> (4 o, _ C' ' d r...::, (45) ', <> ' <> ' <> ' cr o, j/ 0 ' ".. ' <> _ "" <> _ LB Gt St ḠA BA GB GB BB BB RG! (50) ' O Kl ACKS 4 O NERRUPER MOOR NOE 2) ( r BPN NERNAL PO\l'R UN 280 (55C KSU ONLY) CONN (BLY) 7 >, pg. r /''r (0) (E) <m]..r <> MG (, ""' ')..,. ; r r ( (YBL) 't7 l >r to 0Vt (0Y) BB)t G ( (Y0) B 4 >+ to 8Vt (SBK _ ).., >t A GRD ( 4 2 >+ A BA (BR8K) l 5>t 4;> B GRC + +_ (BK8R) 4 )L <> B BA l LA"" l AMP 24B FUSE AUDBLE SG /2 AMP 24E FUSE 24V DC ALK BA /2 AMP 24E FUSE ] 24V DC SG BA /2 AMP 24E FUSE O EXERNAL PO\l'R (550C KSU ONLY) NSALLER W NG MUL PLED O OlHER ERMNALS ON CONN BLOCK O Kl ACKS 4 NOES:. DASHEO LNES REPRESEN FACORY WRNG. SOLD LNES REPRESEN W RES O BE RUN BY NSALLER AS REQU REO 2. ""EN KS9lB5 L2 24V OC NERRUPER S USED, REMOVE FACORY SRAP BEWEEN lbe A'll 40E ON FRON OF BLOCK: F KSU S 55C, PU SRAP BEWEEN l8e A' 47E. F KSU S 550C, CONNEC EXERNAL O l7d All lbd AS SHO ABOVE l, NUiflERS A'll LEmRS N PARENlHESES ARE FOR REFERENCE. ONLY AND DO NO APPEAR ON BLOCK LOCAED ON FRON PANEL ABOVE NERRUPER. Fig. 5Power Supply Connections for 550/55C KSU Page 0 BSP i0_ jpg Scanned by Frank Harrell, (Cowboy Frank) Castle Rock, Colorado Oct 4, 202 6:42:09

11 SS, SECON O LOCAL GRD 0 24V DC FOR KS NERRUPER (NOE2) O OV± LAMP O AUDBLE SG O ALK BA. FOR MANUAL NERCOM O 2026V DC SG BA. MOOR MG MB OV± G ev± A GRD A BA. B GRD B BA. O BA FREQUENCY RG GENERAOR OR EXERNAL 05V± POWER FOR RNGERS FROM 550B KSU O EXERNAL POWER OV± KS975, L p r j L l 3BE (SRAPPED O 40E GRD 37E (SRAPPED O 39E) 24V DC GRD o E F 37 _.. r 38. ) 39 l : " 43 r : 46.v 47 ' a ) f : l / v, KS93B5,L (MOl r r r f _ PROVDE WHEN 0!5V ± RNGER S NO USED B 0!5V ± KS93B5,L2 3BE!SRAPPED O 470 3BE (SRAPPED O 47F) 37E!SRAPPED O 450) 37E (SRAPPED O 39E) MULPLED O OHER ERMNALS ON CONN BLOCK NOES: * 8PN CONNECOR ) POWER O ACt<S 4 NERNAL POWER UN 28A (55B KSU ONLY),o(G) r <> OV :t l?:> G r +o(bv± l la GRD ( Lo la BA.) l 4>8 GRD <> (B BA.) ] LAMP 3 AMP 248 FUSE AUD SG 2 AMP 24E FUSE 20V AL K BA. /2 AMP 24 E FUSE ] 20 v SG BA. /2 AMP 24E FUSE. DASHED LNES REPRESEN FACORY WRNG. SOLD LNES REPRESEN WRES O BE RUN AS REQU REO, 2. REMOVE FACORY SRAPS BEWEEN 37E AND 39E AND 3BE AND 40E FOR 24V DC KS NERRUPER OPERAON. HE POWER CONNECONS FOR EHER NERRUPER MOOR ARE SHOWN A LEF, * 8 PN CONNECOR AND WRNG O CONNECNG BLOCK FURNSHED N BOH 5508 AND 558 KSU. Fig. 6Power Supply Connections for 550/558 (MD) KSU Page BSP i0_ l.jpg Scanned by Frank Harrell, (Cowboy Frank) Castle Rock, Colorado Oct 4, 202 6:42:30

12 SECON GROUND ERM. ON CONN BLK O LOCAL GRD.!..8!!L ' to'n R Eg;N 6 G 6B B 5 Co'6K (NOE ) 0 E F NERNAL O 24V DC POWER PLAN BA, LS MD KS NERRUPER i. _.. (55A KSU (MD) ONLY) (NOE 2!NOE 2 co N 6 o R LAM/ u O P V?" ] (G) LAMP L$ 4ft _,::<C OV''± = o42;_,t++! <> f _ +...!,!O ) + 3 >+ 3 AMP t<' (OV ±) 248 FUSE t G 43 L <>ft O AUDB LE to K 8 >r (Gl ] AUD SG SG ACK 4 _,8,_,_v = +.: <>;;;:,<> AMP >t t0 (20V:!:) 24E FUSE P r _P_ FOR >+ (A GRO) ] 24V r N A ear 46 ( ALK BA. /2 AMP _::_:::::.:..:.. ++lr+o 6 <> 2 >t (ABA.) 24E FUSE PROVDE WHEN 05V :t p RNGER _;B::...:: G::;Rc:D',i,..++ <7> 4 S O V DC NO USED l >o )i (BGRO) >""L <> SG BA. 48 ] 24V SG BA. /2 AMP...::Bc.;Be,:: A:..:. '. f, H+0 <j> o _ rl <>(BBA) 24E FUSE i.._...:::; RG' 409 r4+ '::o <> _ O EXERNAL l!l_ POWER 50 <> V:t supply FOR ' O ALK BA....: M:.: _ ++4 < o > <> ' + _...'! _ M o O i o N R * G:...:..:: L::.:: : A ::...::,c FOR RNGERS OSv+ O:::, R_:G:.,:: RD l.., :..: l ;_ ]>"" :::f _ +...!,!0 t 7 >r GR D :,:: fy.f; FROM 550A (MD) KSU O EXERNAL POWER <> O KU ACKS 3 MULPLED O OHER ERMNALS ON CONN BLK NOES'. DASHED LNES REPRESEN FACORY WRNG. SOLD LNES REPRESEN WRES O BE RUN AS REQURED. 2. REMOVE FACORY SRAP BEWEEN 40E AND 42E FOR 24V DC KS NERRUPER OPERAON. HE POWER CONNECONS FOR EHER NERRUPER MOOR ARE SHOWN A RGH. * 8PN CONNECOR AND WRNG O CONNECNG BLOCK FURNSHED N BOH 550A (MOl AND 55A (MD) KSU. MOOR OV:t GRD 24V OC GRO KS975, l 42E (SRAPPED O 40E) 4E KS9385, Ll (MD F (SRAPPED O 40F) KS9385, L2 48F (SRAPPED O 40Fl 470 Fig. 7 Power Supply Connections for 550/55A (MD) KSU Page 2 BSP S825A07i0_ jpg Scanned by Frank Harrell, (Cowboy Frank) Castle Rock, Colorado Oct 4, 202 6:44:04

13 SS, SECON PAR <F COONEC NG 8 LOCK O S Al.O SG O 2Ml ALO SG O lrd Al.O StG 0 4H Al.O SG (A) (B) (C) (0) (E) o (2'7) NOES:. DASHED Ll NES REPRESEN FACORY WRNG. SOLD ll NES REPRESEN W RES O BE RN BY NSALLER AS REQURED 2. SRAP ERMNALS AS REQU REO FOR C ON ALOBLE SGNALNG o 0 o (40) LB o 0 o (4) Gt o 0 o (4Z) St o..o o (4l) GA o..o o o (44) BA o..o<t o o (45) GB o o o (46) GB ooo o <> ooo oo o (47) o o (46) <> y (49) o y (50) BB BB RC RB RC 0?/:i O 8A ] QUENCY GENERAOR EXERNAL RP«ilf«i Fig. 8Connections for ndividual or Common Audible Signaling on 550/55 C KSU Page 3 BSP 5825A07i0_ jpg Scanned by Frank Harrell, (Cowboy Frank) Castle Rock, Colorado Oct 4, 202 6:44:25

14 SECON PAR OF COONEC NG BLOCK O S AOO SG O 2NO Al.O SG O lro AOO SG B R B R B R (A) (B) (C) (0) (E)... (27) o o (2B) R R FROM COM AOO AUX COO CK (227YPE K) o<> 0 o o ( 9) o<> oo (40) LB o o oo (4) G oo 0 oo (42) S± NOES:. DASHED LNES REPRESEN FACORY WRNG. SOLD ooo oo (4,) GA Ll NES REPRESEN W RES O BE RUN BY NSALLER o o oo (44) BA AS REQURED 2. REMOVE FACORY SRAPS ooo o o (45) GB FROM FRON OF CONN BLOCK ooo oo (46) GB *PAR OF SA!4: CABLE ooo o o (47) BB ooo oo (48) BB o o ooo o (49) o (50) RG ' RG FREQUENCY 05Vt O BA GENERAOR OR EXERNAL RNGNG Fig. 9Connections for Common Audible Auxiliary Control on 550/55C KSU Page 4 BSP i0_ jpg Scanned by Frank Harrell, (Cowboy Frank) Castle Rock, Colorado Oct 4, 202 6:44:44

15 SS, SECON O S AUD SG 0 PAR OF B&57 CONNECOR BLOCK 27t:? o ooo 27 DASHEO LNES REPRESEN r ' FACORY WRNG. SOLD LNES REPRESEN WRES O BE RUN AS NEEDED. 2<?!... ooo 28 r.' * SRAP ERMNALS FOR COMMON AUDBLE SGNAL. D 2 L 29l * o o o 29 (F REQ r' r r, 30<?+ o oo 30 r+ 0 O SRD AUD SG o oo 3 (F REQ 32<?...6 o o32 0 o 4H AUD SG nt o o33 F R EO ' R " + H : ; : : : : 34 <? _j * o o34 L_r+t, 30<?6<> ooo 30 L LL L_ r :..!!... _ " secr6 o o<)o 36 L l : : L r (,!7<( o <)o37 : L L :; + (LNE3 RC lbj> 6 <> o<>o 38 FROM ACKS 4 j l+',', l =====: : 3 _ 9 o<) 40 _=., 4 o o 4 o.o o 42o.oo ooo42 j 40ooo ==.:: 43ooo o<)o43 44ooo oo o44 4!5o.oo f o o4!5 46o.oo ooo46 47o<><> oo<>47 === _.: 4 o o _:._::=:_ <>48 o o49 9 soo<> o o.<)!50 Fig. toconnections for ndividual or Common Audible Signaling on 550/55A and B (MD) KSU Page 5 SP i jpg Scanned by Frank Harrell, (Cowboy Frank Castle Rock, Colorado Oct 4, 202 6:45:05

16 SECON PAR OF CONNECOR BLOCK <> ooo 27 ooo 28 ooo 29 t Bl O 4H AUD SG (F REO) O COM AUO AUX CON CK (2278 OR 227A (MD) KU) CA CA CA _::::.._ t+tl L : CA t o o o 32 t... 33}o ooo 33.r+ L il 34 j o<><>34 r L t ++., * 35 :: =±== (LNE ) RC o <>35 L ti r ;6t;..r=,Lt:. == :..:: Lt+ * L. 37<(': _::_ :: o:>o37 :: :::: * :.=:_:; L t 38? o <><>38 39.:..= = r:.=== =: (LNE 2) RC (LNE 3) RC (LNE 4) RC FROM COM AUO AUX CON CK (2276 OR 227A (MD) KU) FROM ACKS o o o o 4 0 L 4o o ooo 4 42 oo o o o ooo ooo oo o o oo 44 4sooo ooo4s 46ooo ooo46 l : 47ooo ooo47 l _ = = = : :=== 48 49o<>o o;: ;::t0 49 o 5 0 _> <>_ L, _o rh= 0 o r== = = ==5 DASHED LNES REPRESEN FACORY WRNG SOLD LNES REPRESEN WRES O BE RUN AS NEEDED *REMOVE SRAPS t PAR OF SAME CABLE :::! _,_ O 05Vi GENERAOR... F RE QUENCY ' ' R,_, G K: N L :)N NG Fig. Connections for Common Audible Auxiliary Control on 550/55A and B (MD) KSU Page i jpg Scanned by Frank Harrell, (Cowboy Frank Castle Rock, Colorado Oct 4, 202 6:45:23

17 SS, SECON A DESGNAON SRP A P RNG.,."'' A LEAD LAMP GRD LAMP LEAD LNE DESGNAON SRP B A A A Bl Bl Bl Bl P RNG A LEAD... "'' LAMP GRO LAMP LEAD LNE Z P RNG A.,.,.., LEAD LNE 3 LAMP GRD LAMP LEAD P RNG.,.,.., ] A LEAD LNE 4 LAMP GRD LAMP LEAD 8 OR BZ LEAD BELL OR BUZZER LEADS OR BZ LEAD FOR LNE 8 OR BZ LEAD OR BZ LEAD FOR LNE 2 8 OR BZ LEAD OR BZ LEAD FOR LNE 3 8 OR BZ LEAD OR BZ LEAD FOR LNE 4 CA COMMON AUDBLE CONROL FOR LNE CA COMMON AUDBLE CONROL FOR LNE 2 CA COMMON AUDBLE CONROL FOR LNE 3 CA COMMON AUDBLE CONROL FOR LNE 4 P RNG P RNG P RNG P RNG N COMNG CO OR PBX LNE LNE 2 LNE 3 LNE 4 FOR 550 AND 55 YPE KSU MG MOOR GRD MB MOOR BA. LAMP GRD LB LAMP BA. G± GRO s± AUD SG GA A GRD BA A BA GB B GRD. GB 8 GRD. 8 BA. B BA. RG RNG GRD RB RNG BA. FOR 5506 (MO), 556 (MD) 550C AND 55C KSU LB G! s± GA BA GB RG RB FOR 550A (MD) AND 55 A (MD) KSU MOOR SAR LAMP GRD LAMP BA. GRO AUD SG "A" GRD "A" BA. B GRD B BA. R lng GRD RNG BA, Fig. 2Lead Designations on 550 and 55ype KSUs Page 7 7 Pages BSP i j g Scanned by Frank Harrell, (Cowboy Frank) Castle Rock, Colorado Oct 4,202 6:45:45