Bell System 500A Reference

AT&TCo Standard SECTION 502-501-101, Issue 3, July 1972 REFERENCE 500A/B, 500C/D, 500J/K, 501A/B, 501C/D, 501J/K, 554A/B, 554f, AND 556A/B TELEPHONE SETS 1. GENERAL 1.01 This section provides identification and connection information for general purpose 500-type telephone sets. 1.02 This section is reissued to: • Include D4BT mounting cord • Revise Fig. 8 and Table F Changes or additions in the body of tables are indicated by shaded areas. 1.03 Code numbers such as 500C/D cover both manual and dial versions, respectively, of the same type telephone set to permit converting to either type without changing the code number stamped on the base. The letter R was added to the code number at one time to indicate the set was equipped with a retractile handset cord. 2. IDENTIFICATION 2.01 The 500-, 501-, 554-, and 556-type telephone sets are single line sets for use in common battery areas, manual or dial. 2.02 501-type telephone sets are identical to a similarly coded 500-type set except for the addition of a 3-flement, cold-cathode, gas-filled tube, coded 426A. 2.03 554A/B, F, and 556A/B are standard, wall mounted telephone sets. The 556A/B is the same as the 554A/B except for the addition of a 426A tube. 2.04 The 554F is factory equipped with a 9-foot handset cord. 2.05 The 554-type sets are suitable for A lead control with wiring modifications. 2.06 500C or 554A manual telephone sets can be ordered modified per D-180405 or D-180406 Kit of Parts, respectively. The kit modifies the set for use with semipublic single slot coin telephone set as an extension station. 2.07 All parts of the set enclosed by the housing mount on the metal base. The network and line switch are riveted to the base and are not replaceable. Table A list components of these sets. 2.08 Ringers are mounted to base with two P-43A456 washer head mounting screws in rubber grommets. 2.09 Ringer off position can be provided, when authorized locally, by bending back ringer stop spring to provide a fifth position (OFF) on the ringer volume control. 2.10 The G1- or G3-type handsets in these sets may be replaced by a G6AR (MD), G6B, or D-180413 handset for impaired hearing, a G7AR (MD) or G7B for weak speech, or a G8A (MD) or G8B for noisy locations. Refer to section covering these handsets. 2.11 425A, 4-element tube may be substituted for 426A, to care for cases of excessive power induction. See section entitled Inductive Noise for additional information concerning inductive interference. 2.12 For negative stations in offices without ANI, (R) lead from 426A tube may be connected to G if ringer operation is marginal. 2.13 Tube assembly is held to base of set with single screw (Fig. 3). 2.14 These sets are available in all standard colors as indicated in Section 500-12(}100. Components available in color include the dial or apparatus blank, handset, mounting cord, and housing. @ American Telephone and Telegraph Company, 1972 Printed in U.S.A. Page 1 BSP 502-501-101-i03_1972-07-0l.;pg Scanned by Frank Harrell, (Cowboy Frank) Castle Rock, Colorado Jan 29,2012 23:39:08

APP BLK§§ 95C NET. RINGER C4At:t C4A§ 425Ett C4A HANDSET Gl- or G3-Type • MD ** Includes 311A equalizer t 554F factory equipped with 9-foot handset cord tt Replaces 425B network t Replaces 7C or 7D dial tt Early models had C2A ringer §Early models had C3A ringer §§Replaces 95A or 95B apparatus blank Fig. 1-5008, D, K, or 5018, D, K Telephone Set '1 Page 2 Components other than the housing must have the code completed by adding the desired color suffix. The housing P- number must have the desired color suffix substituted for its last two digits. Note: •The D4BT universal mounting cord is available in ( -29) transparent only .• 3. INSTALLATION AND MAINTENANCE 3.01 Refer to Section 502-500-110 for common installation and maintenance information SSP 502-501-101-i03_1972-07-02.Jpg Scanned by Frank Harrell, (Cowboy Frank) Castle Rock, Colorado Jan 29,2012 23:39:41

P-43AI06 SCREW Fig. 3-501-Type Telephone Set, Tube Assembly Fig. 2-554- or 556-Type Telephone Set With Hondset in Waiting Position SSP 502-501-101-i03_1972·07-03.jpg Scanned by Frank Harrell, (Cowboy Frank) Castle Rock, Colorado Jan 29, 2012 23:40:13 r Page 3

(NOTE 3) TIP PARTY IDENT GROUND NEGATIVE (-) POSITIVE <+l TIP PARTIES PARTIES WIRE INDIV PARTY RINGER REV. (NOTE 4) OR COLOR OR RING NO NORMAL WHEN CONN LEAD PARTY CONNECTIONS TO L.L. EQUIP. ·- BRIDGED I DENT (NOTE 2) GRD RING TIP RING TIP (1-S) (2-6) <3-n (4-8) 1000!) 2650!l 1000!l 2650!l R K K K K M R G E E A A Ringer BK G G G G R M K E "E K K Leads s E E E M K G R K K E E S-R E E E R G K M A A E E Line Switch s L2-A L2-A L2-A A A A A A A A A 426A Tube R Ll or G Ll or G A A BK G G E E (3-Element) y E E G G Mtg R L2 L2 L2 L2 L2 L2 L2 L2 L2 L2 L2 Cord G Ll Ll Ll Ll Ll Ll Ll Ll Ll Ll Ll in Set y G G G G G G G G G G G Mtg R R R G G G G G R G R G Cord at Conn G G G R R R R R G R G R Blk y G y y y y y y y y y y Line Ring R R R R R Wire R R R R R R R at Tip G G G G G G G G G G G G Conn Blk Grd y y y y y y y y y y y y Notes: 1. To silence ringer permanently: (a) For all classes except tip party identification, connect (Y) mounting cord to same terminal as (R) mounting cord lead at connecting block. (b) Tip party identification: • For lOOO!l ground remove (R) from K of network and insulate and store on unused terminal. • For 2650!l ground remove ( S) from K of network and insulate and store on unused terminal. 2. If bell taps on stations connected to long line equipment, use these connections to retain party ground identification. 3. When grounded ringer arrangements are used with 96 volt long line circuits, a D-180036 ·ringer isolator must be used. 4. See Note 5, Fig. 4. Page 4 SSP S02-501-101-i03_1972-07-04.jpg Scanned by Frank Harrell, (Cowboy Frank) Castle Rock, Colorado Jan 29, 2012 23:40:35

WIRE OR LEAD Ringer Leads Line Switch Lead 426A Tube ( 3-element) Mtg Cord in Set Mtg Cord at Conn Block Line Ring Wire at Tip Conn Grd Block Notes: TABLE C 500C/D AND 501C/D TELEPHONE SET LINE, RINGER, AND TUBE CONNECTIONS (NOTE 3) NEGATIVE (-) TIP PARTY !DENT GROUND PARTIES TIP (NOTE 4) INDIV RING PARTY COLOR OR NO RINGER REV. BRIDGED PARTY I DENT NORMAL WHEN CONN GRD CONNECTIONS TO L.L. EQUIP. RING TIP (NOTE 2) (1·5) (2-6) - 10000 26500 10000 26500 R L2 L2 L2 K B B G G G BK G G G G B B K G G s K K K B K G B A A S-R A A A B G K B K K s L2 L2 L2 A A A A L2 L2 R Ll or G Ll or G BK K K y L2 L2 R L2 L2 L2 L2 L2 L2 L2 L2 L2 G Ll Ll Ll Ll Ll Ll Ll Ll Ll y G G G G G G G G G R R R G G G G G R G G G G R R R R R G R y G y y y y y y y y R R R R R R R R R R G G G G G G G G G G y y y y y y y y y y 1. To silence ringer permanently: POSITIVE ( +) PARTIES RING TIP (3-7) (4-8) L2 L2 L2 L2 A A K K L2 L2 L2 L2 K K G G L2 L2 Ll Ll G G R G G R y y R R G G y y (a) For all classes of service except tip party identification, connect (Y) mounting cord to same terminal as (R) mounting cord lead at connecting block. (b) For tip party with 1000 ohms identification ground; remove (R) ringer from K of network and insulate and store on unused terminal. (c) For tip party with 2650 ohms identification ground; remove the (S) ringer lead from K of network and insulate and store on unused terminal. (d) For the 501C/D telephone set connect (Y) mounting cord lead to same terminal as (R) mounting cord lead at the connecting block. 2. If bell taps on stations connected to long line equipment, use these connections to retain party ground identification. 3. When grounded ringer arrangements are used on 96 volt long line circuits, a D-180036 ringer isolator must be used. 4. See Note 4, Fig. 6. Page 5 SSP 502-501-101-i03_1972-07-0S.;pg Scanned by Frank Harrell, (Cowboy Frank) Castle Rock, Colorado Jan 29,2012 23:41:09

ª{ I I @!j (Y) I I I --.;iitr-------,‚#!ƒ1;... . .'..:::!.._i_:_}j I I I I I I I I I I I -i!+------'"11;;;. "181!1•9::.!....::_: }1:: Et (S) Tl P CONN BLK RING GRD Tl P RING GRO (Y) (Y) C4A RINGER AND 426A TUBE NEGATIVE RING PARTIES (S·R) (R) l

ll NE SWITCH (S-G} d e (5 -Rl IS-R I (S-W) g.{. I <' 425A (MD} NETWORK ' 311A EQUALIZER df: L2 A K E G * 121 0---j E---121 121 121 ) I (NOTE 4} 1!11 -, (BL) I g(NOTE I}- 1/ ·:I I '' _j I 1 l.---+-, 7 Rt Mt I i~ I r._,:_!··.i."_;r:C·:,_.i.i_!_.-.::·:.1 . Rw lli\1 .Ĭ\d• .A- :; r.til ttn€ ::,ī3: Gl- OR G3- TYPE HANDSET (W) (w) L RCVR (R) ?J TRMTR : (BK) (S-Y) (S) (S) NOTES: • •r T I 4 Ĩ lf.t.' ‘’ L---a- .. -...J ~r f'_h_;_:_:_=.•.r.:i-j-- mi -ĩĪ I. FOR MANUAL SERVICE, MOVE (S-BR) LEAD FROM r T O RR TERMINAL 2. 500 A/B SET FACTORY-WI REO FOR RING PARTY. 501 A/B SET FACTORY-WIRED FOR NEGATIVE RING PARTY. SEE TABLE B FOR CLASSES OF SERVICE NOT SHOWN. 3. ll NE S\11 TCH OFF-HOOK SEQUENCE: (I) ab BREAKS (2) de MAKES (3) be MAKES (4) f g BREAKS 4. 425A NETWORK INCLUDES .311A EQUALIZER. 5. STATIONS WITHOUT ANI,(R) TUBE LEAD MAY BE CONNECTED TO G IF RINGER OPERATION IS MARGINAL. AT NEGATIVE STATIONS ON 96V LONG LINE CIRCUITS, t R) TUBE "LEAD SHOULD BE CONNECTED TO G. SAME TERMINALS MAY APPEAR ON RINGER CONNECTION. OP- DIAL PULSE CONTACTS ON DIAL OFF- NORMAL CONTACTS TPA-542628 Fig. 4-500A/B (MD) and 501A/B (MD) Telephone Sets, Connections (Sheet 2 of 2) Page 7 SSP S02-501-101-i03_1972-07.{)7.jpg Scanned by Frank Harrell, (Cowboy Frank) Castle Rock, Colorado Jan 29, 2012 23:42:02

IOENT GRO (S) A 1\:'-o--;..+: 9 _;;:_i: } 5 i ··::" ,·:s [W 67i . (S) . I I £\j ' I I I POSITIVE RING PARTIES GRO I y t}(Y) I L_ ______ ----- Fig. 5-500J/K (MD) and SOIJ/K (MD) Telephone Sets, Connedions (Sheet I of 2) BSP S02-501-101-i03_1972-07-08.jpg Scanned by Frank Harrell, !Cowboy Frank) Castle Rock, Colorado Jan 29,2012 23:42:23 TO f- SH.2 I I I Ĺ I I I I I _j TPA 542629

Ll L2 A K E G ( 0 0 0---1E---0 0 0 ) i.'.: .. '.!,, ,ĸ, t 1'4' ,, :: G "', , , I _J I l ""l_ ć(S-BK) t.i.·.·.·.:.. ħ- ,-,. . 7 R* I 1 *Ķ II RR M'* / .--4§¨©-------++-------------------' (S-R) (S-R) i{| ON (w l xyf ]f1*·ĈĉĊċČ¥$č { -G-N-----------------------' I (w) ;;;;ll m:;:.;: ::tt: ISS 3, SECTION 502-501-101 I I i i I TERMINAL BLOCK •• ef k,,:. : .. v ... w.} .. ‰·:.:.Š I ķ"' I S i Gl- OR G3-TYPE HANDSET (\1) A l Ď---(_s_-B_K_) __ -+.m#lli‹ ------Œ}ffim--------------------------rŽMf •d .·.:$ :.· . .. . '.:ĵ· ___ RW ďĐđĒ-- --ēĔ#10ĕ : _______ 1R_ I __ Ĵ -;1J TRMTR (S-W) I zff c Ifu ij!\ ,-- r----5:6ffiww47,,-s--w-)-----m3e;8------jf II :: II (Wl :::.() R CVR (s-Y) (S) (S) NOTEc I, (S-BR) SWITCH LEAD IS CONNECTED TO F TERMINAL IN DIAL SETS AND TO RR TERMINAL IN MAifJAL SETS. 2. 500 J/K SET FACTORY-WIRED FOR RING PARTY. 501 J/K SET FACTORY-WIRED FOR NEGATIVE RING PARTY SEE TABLE 8 FOR CLASSES OF SERVICE NOT SHOWN. 3. LINE SWITCH OFF-HOOK SEQUENCEc (I) ob-BREAKS (2) de-MAKES (3) be-MAKES (4) fq-BREAKS *SAME TERMINALS MAY APPEAR ON RINGER CONNECTION. IBK} DP- DIAL PULSE CONTACT ON -DIAL OFF-N ORMAL CONTACT Fig. 5-500J/K (MD) and 501J/K (MD) Telephone Sets, Connedions (Sheet 2 of 2) TPA 54 2629 Page 9 BSP 502·501-101-i03_1972..07-09.jpg Scanned by Frank Harrell, (Cowboy Frank) Castle Rock, Colorado Jan 29, 2012 23:42:57

RING R .,, .. (G) TIP l f (R) Fig. 6--SOOC/D and 501C/D Telephone Sets, Connedions (Sheet 1 of 2) Page 10 BSP S02-501-101-i03_1972-07-10.jpg Scanned by Frank Harrell, !Cowboy Frank) Castle Rock, Colorado Jan 29,2012 23:43:19

FROM SH I -- ..:__ (S'-'-) ___ , (Y ) I S-Y] 1 9C, 7C (MD), OR 70 (MD) I 425B (MD) OR 425E NETWORK . DIAL . • rc' I &.b !1'/(W ) i;jj I II I s-w] Mil !NOTE 11 (BL) h/j qr I ;::r' DP II ,i--. '% I # T, I (BL OR G) ur& '-..,.. RR (BR) IS-BR] IW< GN ISS 3, SECTION 502-501-101 I G 1- OR G3- TYPE ' "'" " I .;lt] (W) 'a 1I ... ',! ... .. ˆ ... t.! .. !J}(R l ls-R] '? *BU-----+-+-ZM+(B=K[)-- NOTES: p(BK )[S-BK) I ¡(¢ W£)¤¥--------------------¦ bR ON* (wl ·9 st 'M fu i%i I • FOR MANUAL SERVICE, MOVE (W) I S-W) LEAD FROM F TO RR TERMINAL, 2. 500 C/O FACTORY WIRED FOR RINC. PARTY. 501 C/0 FACTORY WIRED FOR NEG AT I VC R ING PARTY. SEE TABLE C FOR CLASSES OF SERVICE NOT SHOWN. 3, L I Nf SWITCH OFF HOOK SEQUENCE: (I) ab BREAKS (3) be MAKES (2) de MAKES (4) IQ BREAKS 4. STATIONS WITHOUT ANI, ( R) TUBE LEAD MAY BE CONNECTED TO G IF RINGER OPERATION IS MARGINAL. AT NEGATIVE STATIONS ON 96V LONG LINE CIRCUITS, (R) LEAD SHOULD BE CONNECTED TO G. * SAME TERMINAL MAY APPEAR IN RINGER CONNECTIONS. ( ) CURRENT COLOR CODE [ ] MD COLOR CODE DP-DIAL PULSE CONTACT ON-DIAL OFF-NORMAL CONTACT Fig. 6-500C/D and 501C/D Telephone Sets, Connections (Sheet 2 of 2) BSP 502-501-101-i03_1972-07-ll.jpg Scanned by Frank Harrell, (Cowboy Frank) Castle Rock, Colorado Jan 29,2012 23:43:48 TPA Ħ42630 Page 11

j TIP (G) ff LQ j); (NOTE 2) iF (G) (S-G] } R I NG;'-'( R"-)ý··.,:·: ...... .. f-rl'-{ 22}--4;;!*';i-: ----ii*- ( Yr)_:_( S_ -_Y.:_] :u···· \ ', · .•.•.•. •.•.•.•.••..• (S) •. , ••.•••. (R) RING (R TIP (G) GRD I Y) RING(R} Tl P (G) GRD (Y) t 2650n •••••••••• (S) 10000 BRIDGED Ll ģ Ĥ L2 ';: fK (R) B n. G ,.., IOOOn Tl P PARTY I OOOn I DENT GRD Ll L2 .fA ;,. ` B fA G _/"> (S) (BK) j • o (R) l'o! (S-R) j TIP PARTY, 265011 I DENT GRD :: :::: J, (S) (G) (S-G] (Y) (S-Y] (S) LINE WIRE :¥! 556A/B TERþ. :{:::• C4A ON NET • ž!!!}Ÿ (s-Gj TIP ÿIGĀ)ā-----+' i;Ă--ă3--ff----Ąff-'-ąĆ l ĥ:::::··· RING (R)----4':+- --f?--- (5-Y] TIP R lNG REVERSE FOR Tl P PARTY SERVICE (G) (R) REVERSE FOR TIP PARTY SERVICE AND TIP PARTIES TO }- SH.2 I I __ _j TPA 542631 Fig. 7-554A/B, F and 556A/8 Telephone Sets, Connedlons (Sheet 1 of 2) Page 12 BSP 502-501-101-i03_1972-07-12.jpg Scanned by frank Harrell, (Cowboy Frank) Castle Rock, Colorado Jan 29, 2012 23:44:10

FROfo4 SH. I LINE SWITCH (G I [ S-G] (Y)(S-Y) d e (W) 9C,7C !MDI OR 7DIMOI DIAL js-w) 425E OR 4258 (MOl NETWORK gh1i ġt:Ģ .f:H Ill jk:lmn j¥- (NOTE I) lit GI- OR G3-TYPE HANDSrT 1 r • ::g (w) (f BC::. L'- ) ---f*£m'--i;--e; r-:-------{OJ"'):')Il ,---filif-i__:_:.:_---(}: RCVR OP l “ :œ / { |}~ +€ TRMTR .__<_o_o_• _ BL+! ...• i'- , _l'-:e-+OPAAA. · . ·c=:; UV; g;;: RR ¥H (BR) n; tt:: N . - (S·BR) (s) 1-: iii ;;; (BK) !+'-‚;ƒ„-)-%…. :W:-X:YZ-[---f\f!--------G N]^-+-_ (w) )} NOTES: I. FOR MANUAL SERVICE, MOVE (W) [S-WJ LEAD FROM F TO RR TERMINAL. 2. 554A!B, F IS FACTORY WIRED FOR BRIDGED SERV ICE, 556.4./B IS FACTORY WIRED FOR NEGATIVE RING PARTY, FOR CLASSES 'Of SERVICE NOT SHOC .. REfER TO TABLE Q, 3. LINE SWITCH OFFDHOOK SEQUENCE: (I) be-MAKES (3) ob-BREAKS (2)de-MAKES (4) gf-BREAKS 4. STATIONS WITHOUT ANI, (A) TUBE LEAD MAY BE CONNECTED TO G IF RINGER OPERATION IS MARGINAL. AT NEGATIVE STATIONS ON 9611 LONG LINE CIRCUITS, {A) LEAD SHOULD BE CONNECTED TO G. l CURRENT COLOR CO.OE ( ) MO COLOR CODE OP-DIAL PULSE CONTACT ON-DIAL OFF-NORMAL CONTACT TPA 542631 Fig. 7-554A/B, F and 556A/B Telephone Sets, Connedions (Sheet 2 of 2) SSP 502-501-101-i03_1972-07-13.jpg Scanned by Frank Harrell, (Cowboy Frank) Castle Rock, Colorado Jan 29, 2012 23:44:39 Page 13

(NOTE 3) WIRE OR COLOR LEAD R Ringer BK Leads s S-R Line Switch s 426A Tube R BK (3-Element) y Line Wire Ring R in Tip G Set Grd y • No ground required Notes: 1. To silence ringer: TIP INDIV RING PARTY OR NO BRIDGED PARTY I DENT GRD L2 L2 L2 L1 G G K K K A A A L2 L2 L2 L2 L2 L1 L1 L1 L2 G* G G NEGATIVE (-) POSITIVE(+) TIP PARTY IDENT GROUND PARTIES (NOTE 4) PARTIES RINGER REV. NORMAL WHEN CONN CONNECTIONS TO L.l. EQUIP. RING TIP RING TIP (NOTE 2) (3·5) (2-6) (3·n (4-8) 1000fl 2650!1 1000!1 2650!1 K B B G G G L2 L2 G B B K G G L2 L2 B K G B A A A A B G K B K K K K A A A A L1 or G L1 or G L2 L2 K K K K L2 L2 G G L1 L1 L1 L1 L2 L1 L2 L1 L2 L2 L2 L2 L1 L2 L1 L2 G G G G G G G G (a) For the 554A/B and F telephone sets for all classes of service except tip party grd. identification, connect (S) and (BK) ringer leads on K terminal of 424E network. (b) For tip party with 1000!1 identification ground, remove the (R) ringer lead from K of network and insulate and store or connect to spare terminal. (c) For tip party with 2650!1 identification ground, remove the (S) ringer lead from K of network and insulate and store or connect to spare terminal. (d) For the 556A/B telephone set, connect (R) and (BK) ringer leads to K terminal of network. 2. If bell taps on stations connected to long line equipment, use these connections to retain party ground identification. 3. When grounded ringer arrangements are used on 96 volt long line circuits, a D-180036 ringer isolator must be used. 4. See Note 4, Fig. 7. Page 14 BSP 502-501-101-i03_1972-07-14.;pg Scanned by Frank Harrell, (Cowboy Frank) Castle Rock, Colorado Jan 29,2012 23:45:00

!NOTE II 3 (RI Cl 0 1 A (S-R} yz ., 2 0 f " 05 (SI 06 x§ K (NOTE II 4 ·IBK) 0E1 E2 RING 0 ll AI(GRD) ³ G A ³ L2 I CONVERSION TO "A" LEAD CONTROL (CURRENT COLOR CODE) (SEE TABLE E) CONVERSION TO •A• LEAD CONTROL (MD COLOR CODE) (SEE TABLE F) ' I a· ( G) IBR) (Y) (S) LINE SWITCH d • *c b 0 f+ e+ (NOTE 5 I (W) (R) IBK) w- I I I I I I I (S-BR)} J [S-R] [S-BK] fu"\\ 9C, 7CIMOI OR (NOTE 41 425E OR 425B(MDI Gl-OR G 3- f.. 70(MO) DIAL /_ F NETW²K HANDSET R !WI I\--- m # A " IBLI JL TYPE RCVR l TE-1 I r " S· DP I TRMTR I M (G OR BLI l vw $, RR J (W) [S-BR] c IBKI - (W) ON :{ (W) GN (W) " .. (R) [S-R] '·' m (BK) [S-BK] .• I NOTES: I. TO TIP AND RING FOR INDIVIDUAL LINE RINGER OR TO COMMON AUDIBLE SIGNAL LEADS FROM EQUIPMENT CABINET. 2. WHEN RINGER IS USED AS COMMON AUDIBLE, CAPACITOR CAN BE REMOVED BY CONNECTING (S) RINGER LEAD TO A OF NETWORK. 3. MOUNT P-338886 TERMINAL STRIP W ITH P-3 38888 RETAINER AND P-294615 SCREWS. IF THE ABOVE ARE NOT AVAILABLE, CONNECT RINGER LEADS WITH 0-161488 CONNECTORS. INSULATE AND STORE TO AVOID MECHANICAL INTERFERENCE. 4. FOR MANUAL SERVICE, CONNECT TIP OF LINE TO RR TERMINAL OF NETWORK. 5. LINE SWITCH OFF-HOOK SEQUENCE: ( 1) bc.MAKES 13) ab BREAKS ( 2) de MAKES ( 4) IQ BREAKS 6. IN SETS WIRED ACCORDING TO MD COLOR CODE, SWITCHING SEQUENCE IS REVERSED TO PREVENT FALSE HOLDING CONDITION WHEN HANDSET IS RESTORED, SWITCH CONTACTS be MUST BREAK BEFORE de BREAK. ) CURRENT COLOR CODE. [ ] MD COLOR CODE. OP- DIAL PULSE CONTACT ON-DIAL OFF-NORMAL CONTACT B- 1 88107 'V a ca .fig. 8--554A/B and F Telephone Sets, Modification for "A" Lead Control. • ;;; BSP 502-S01-101-i03_1972..07-15.jpg Scanned by Frank Harrell, (Cowboy Frank) Castle Rock, Colorado Jan 29, 2012 23:45:30

MODIFICATION FOR "A" LEAD CONTROL CURRENT COLOR CODE REMOVE CONNECT TO WIRE OR LEAD Line Switch Ringer Leads Line Wire in Set Page 16 16 Pages w BR R BK Ring Tip "A" Lead Al-Grrl FROM NET. NET. TERM. STRIP F c c G L2 3 G 4 Ll F L2 G TABLE F 554A/B TELEPHONE SET MODIFICATIONS FOR "A" LEAD CONTROL MD COLOR CORE REMOVE WIRE OR LEAD FROM Line Switch Ringer Leads Line Wire in Set [S-W] (R) (BK) Ring Tip "A" Lead Al-Grd ( ) Current color code [ ] MD color code. NET. F L2 Ll SSP 502-501-101-i03_1972-07-16.jpg Scanned by Frank Harrell, (Cowboy Frank) Castle Rock, Colorado Jan 29,2012 23:45:50 CONNECT TO NET. TERM. STRIP G 3 4