518-410-300_i36a telephone system selector only arrangement

7/27/2019 518-410-300_I36A Telephone System Selector Only Arrangement

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BELL SYS TEM PRACTICES

AT &TCo Standard

SECTION 51 8-410-300

Issue 3, December 1972

6A KEY TELEPHONE SYSTEM

SELECTOR ONLY A R R AN G E MEN T

MAINTENANCE

CONTENTS PAGE

1. INTR ODUCTION

2. GENERAL

3. LINE SEIZURE, Fig. 1 4

4. BASIC OPERA iON OF SELECTOR CIRCUIT,Fig. 2 . . • • . • • • . • . 5

5. STA iON SELECTION, DIALING SINGLE-DIGIT

CODE . • • . • . • . 6

6. S TAT IO N SELECT ION , DIALING 2-DIGIT

CO DE, Fig. 3 . . . . . . . . 7

7. STATION SELECTION, USING SIGNAL KEY

7

8. TA LKING PA TH, Fig. 4 9

9. AUDIBLE SIGNALS, Fig. 5 10

10 . VISUAL SIGNA LS, Fig. 6 13

11. PRESET CONFERENCE, Fig. 7 14

12 . A DD-O N CONFERENCING, Fig. 8 17

13 . OA=-PREMISE STATION, LINE SEIZURE, Fig. 9

• . . • . • . . . • 19

14. OFF-PREMIS E STATION, INCOMING CAL L,

Fig. 10 20

15. OFF-PREMISE STATION, ANSWERING

INCOMING CALL, Fig. 11 . • . 22

1. INTRODU CTION

1.01 Th is section covers the maintenance of the

selec tor only arrangement of the 6A K eyTe lephone System, the use of sequence ch arts andopera tional sketches, and a description of th e

symbols used.

2. GENERAL

2.01 Th is section is reissued to updat e sequenc e

charts an d operational sketches .

2.02 This issue of the se ction is b as ed on CD-

an d SD-69286-01, Issue 8D. If th is sectio n

is to be used with equipm ent or apparatus reflecting a later is sue of th e draw in g, reference shoul d bemad e to the later CD and SD to determine the extent of the ch anges and the m anner in which the section may be affected.

2.03 The circuits used in the

6AKey TelephoneSystem have been reduced to simplified

sequen ce charts and operational sketches.

• Sequence charts cover the op era t ion andre lease of relays, ke ys, and ot her appara tus

in th ei r relative time order. They ar eshown from th e top downward an d ar e co nnected by appro priate lines to sho w the

interdependence of the successiv e operations.

• Operational sketches show complete circuits

fro m battery to g roun d in simplified for m ,completely disregardin g boundaries ofco nventional SD drawings. Key telephon e

unit numbers beneath the co mplete circuit

id en tify key te lephone units in which theindividual relays, relay contacts , or otherap paratus ar e located.

@ Amer ican Telephone and Telegraph Company, 1972

Pr inted in U.S.A. Pa ge 1



SECTION 518-410 -3 00

USE OF SEQUENCE CHARTS AND OPERATIONAL

SKETCHES

2 .0 4 Afte r it has been determined that th e trouble

is in the 6A equipmen t, proceed as follows:

• W at ch relay op era t ion of equipment andco mpa re it to that of th e seque nce ch arts

as show n on the various figures.

• W he re circuit failure occurs, the ope rationa lsk e tc h e i ther will show the com plete path

for the circuit tha t failed or it will re fer to

th e figure where th e complete path may be

found.

2 .05 The fo llowing are sa m pl es of some of the

symbols used in th e preparation of the seq uence charts and op erational sketches contained

in this practice.

SEQUENCE CHART SYMBOLS

t

t_L

T

f: y·

Relay or other apparatus

in a fully op erated posi

tion.

Relay or other ap paratus

in an unoperated or nor

mal position.

Ti me de la y circui t (time

will be designated).

Operation of relay A

causes the op era t ion of

relay B

Both relay s A an d B hav e

to be operate d before re

la y C can operate .

O p era t io n of either theA or B relay will cause

the ope ration of re la y C.

®__l_®

Y' H

B

D

Option: R el ay A, in op

erating, operates rela y

B or C de pe nding on the

wiring option prov ided .

Relay B or C in operating

wo uld in turn op erate re

lay D.

Both relays A an d B must

operate before re lay D

ca n operate. The arrow

is used to ind icate one

w ay action. In this illus

tration, relay C operate s

from relay A only.

OPERATION AL SKETCH SYMBOLS

--o-

X

Relay core an d winding.

A pp aratus oper ated (keys,

telephon e sets , etc).

A pparatus norm al. (keys ,

te lephone sets, etc).

Make contac t of an op er

ated w ire-spring-type re

lay . Relay will be desig

na ted above and contact

nu mber below. The posi

ti on of the number ind i

cates the location of the

fixed contact in the cir

cu it.

Make co ntact of an oper

ated relay having a top

an d bo ttom pile up . Re-

lay w il l be de signated

above and a contact num

ber on each side. Lette r

T or B would indicate

that the contacts are in

the top or bo ttom pile up,

respectively.

N orma ll y closed ·c ontact

of an unoperated wire

spring-type re lay. Rel ay

will be designated above

and contact number be

low.

(

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Normally closed contact

Aof an unoperated relay

I 12 T having a top and bottompile up. Relay will be

designated above and a

contact number on eachside.

2 : ~ Battery symbol.

•I Ground symbol.

TS Point of termination, ter-B

---e-minal strip B, terminal 19.

2.06 A description of the operation, supplementingthe sequence charts, is provided to specify

the functions of the equipment.

2.07 General maintenance of telephone sets, dials,keys, relays, power plants, etc, used with

ISS 3, SECTION 518-410-300

the 6A Key Telephone System is no t covered inthis section. References should be made to the

sections pertaini ng to these specific items.

2.08 The following wiring options are applicable

to thi s section.

WIRING OPTION

XWithout Transfer Circuit (max nine

codes)

w With Transfer Circuit (over nine codes)

HUnder 40 Lamps on System (without

aux relay busy lamp circuit)

MOver 40 Lamps on System (with aux

relay busy lamp circuit}

RLong Line Circuit Associated with

Preset Conference Circuit

K System with Preset Conference



SECTION 518-410-300

3. LINE SEIZURE

3.01 The T and R leads of a 6A Key TelephoneSystem station are connected to battery and

ground through the windings of the A relay. Asa station picks up, relay A operates and causesthe operation of relay B. Relay B in operatingcauses the busy lamps, i f provided, to light steadilyat all stations.

ROH

A26V(A)

OPERATIONAL SKETCH

SEQUENCE CHART

ROH

A

B

BUSY LAMPS

AL L STATIONS

.._---207B OR c------.J ~ - - - - 2 0 7 B O R C - - - - - - - - - - ~

B

BUSY LAMPS

ALL STATIONS

26V(B)

~ - - - - - - - - - - - 2 0 7 B O R C - - - - - - - - - - - - - - . J

(SEE FIG.6)

Fig. 1-Line Seizure

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ISS 3, SECTION 518-410-300

4. BASIC OPERATION OF SELECTOR CIRCUIT S EQ UENCE CHART !SEE NOTE!

4.01 Relays A and Bhave previously been operated

as described in 3. As each digit is dialed,

relay A releases and reoperates in unison wi th

the d ia l pulses. Slow release relay B remainsope rated during dialing. As the A relay pulses, a

ground is connected to th e ro tary magnet causin g

th e selector switch to step in unison wi th the dialed

pulses.

4. 02 A slow re leas ing relay C operates on the

first release o f relay A and rem ai ns operated

during the pul se train. This rela y causes operation

of the T relay whi ch in turn connect s a resistor

and capacitor across its winding. The capacitor is

charged during puls ing, and it s discharg e after

the release of re la y C holds the T re lay operatedfor appro x im ately 1-1/2 seco nd s, thus providin g

the timing interval used to cont ro l the au dib le

signal to the called station.

FIRST DIAL _IPULSE--,

SELECTOR

SWITCH

(STEPS TO

CON TACT ll

OFF-NORMAL

CONTACTS

INTERMEDIATE

DIAL PULSES

1

A

ROTARYMAGNET

ROTARY

MA GNET

A

ROTARY

MAG NET

c

T

SELECTOR SWITCH

(STEPS TO NEXT SUCCEEDIN G

CONTACT FOR EACH OPERATION

OF ROTARY MAGNET

A

ROTARYMAGNET

SELECTOR

SWITCH(STEPS TOCONTACT I)

OFF-NORMALCONTACTS

c

T

NOTE:

COMPLETION OFPULSE TRAIN

OPERATIONAL SKETCH (SEENOTEI

26V(B )

26V(B l

26 V(Bl

1---- - - -2078 OR C - - - - - - ~

~ - - - - 2078 OR C - - - - ~TS

B

ROT.

MAG

TS

B

le-------2078 OR C - - - - - - ~SEL ECTOR OPERATION IS DIFFERENT WHEN A "TOUCH-TONE" ADAPTER

IS IN THE SYSTEM AND A "TOUCH-TONE" DIAL INTER C OM STATION

ORIGINATES A CALL.

Fig. 2-Basic Operation of Selector Circuit Using Ro tary Dial

(TO FIG. 3, 7, 10 )OR PART 5.

Page S



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8. TALKING PATH

8.01 The calling station has selected and signaled

the called station as described in 5, 6, or

7.

8.02 The called station responds to the audiblesignal and connects its telephone circuit to

the T and R leads. Both stations are now connectedto a common T and R path with talking battery

being supplied through the windings of the A relay.

SEQUENCE CHART

ROH CALLING STATION

l ALLEDI TATION ANSWERS

OPERATIONAL SKETCH

ROH CALLING STATION

ANSWERSALLED STATION t

26 V(A)

NOTE: AS THE CALLED STATION

ANSWERS, IT IS BRIDGED TO THE

CALLING STATION AT THE

"A" RELAY

CALLING STA

CALLED STA

'-1•-- 20 7 B OR C ------.j j . -TEL SETS --I

Fig. 4-Talking Path

ISS 3, SECTION 518-410-300

~ - - - - - 2 0 7 B O R C - - - - - - ~

Page 9



SECTION 518-410-300

9. AUDIBLE SIGNALS

9.01 A separate signal pair is required to operatethe audible signal.

DIALING SINGLE-DIGIT CODE

9.02 The release of relay C (as described in 5)

connects audible signal power to the calledstat ion's audible signal: under control of relay in

the selector circuit, the second bank of the selectorswitch, and all normal TR relays (i f provided).

DIALING 2-DIGIT CODE

9.03 The release of relay C at the end of the

second digit (as described in 6) connectsaudible signal power to the called station's audiblesignal: under control of relays in the selector

circuit, the second bank of the selector switch,and the operated TR relay.

SEQUENCE CHART

Page 10

DIALING SINGLE DIGIT CODE

TO PART 5. {SEQUENCE CHART)

II

nAUDSIGCALLEDI STATION

II

TO PART 5. (SEQUENCE CHART)

DIALING 2-0IGIT CODE

TO FIG. 3 TO FIG. 3

AUO SIGCALLED

STATION

I-t-c

TO FIG. 3

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AUD SIG

PO W ER

SUPPLY

X OPTION

OPERATIONAL SKET C H

B

36,37

OR38

RGI

207 8 OR C - - - - - - - - - - - - ~ 1- 2078 OR C ---1

TOPA RT

5 (S EQUENCE)

I CH ART

I

II

1 CALLED W OPTIO N SE E TABLE Bn AUDSIG

I STATION

I D IALING SINGLE DIGIT CODE

TOPART 5

(SE QUENCE)

CHART AU D SIG

POWER

SUP PLY COL A COL B COLC

( . . . . - - - - - - - - - 207 6 OR C _________ ..,,__ ___ ST 216A-----

AUD SIG

PO WERSUPPLY

TS TS STATIONL R G ~ ~ · · ~ 6,37,OR 38

1- -- 207 6 OR c--f

TR TR

CO L C COL B CO L 1'- - - -S E E TABLE C __JJ

--- -TWO 216A P ROVIDED

COR R

'-""""---- 3RD 216A -- -- -. 1<1-- -- -- 2ND 216A - - - - - .



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ISS 3, SECTION 518-410-300

10. VISUAL SIGNALS SEQUENCE CHART

10.01 Relays A an d B operate on pickup as

described in 3. The operation of the Brelay closes the lamp battery supply path to lightthe busy lamps at all associated stations.

ROH

® t:®~

MS

BUSY LAMPSALL STATIONS

ROH

B (SEE FIG. I)

At (SEE FIG. I)

@ ® LAMP__ ., POWER

BUSY LAMPS

ALL STATIONS

TABLE E

COL A COL B

TERM. OPR CONT

211 8

27 6

29 10

30 II

SUPPLY

LAMP

26 V

(B)

POWERSUPPLY

COL C

TERM.

23

26

37

39

LAMPS BUSY LAMPSTATIONS ALL STATIONS

OPERATIONAL SKETCH

H OPTION (WITHOUT AUX RE L BUSY LP CKT)

1 - - - - 2078 OR C -------+1 1---- 2 0 7 B O R C ~

M OPTION (WITH AUX REL BUSY LP CKT)

8

\--------111

I + - - 2.27A OR B - - - - ~ t - - - - - - 2 . 0 7 B OR C - - - ~

TABLE E TABLE EBUSY

TABLE ECOL A

MS COL CLAMPS COLD

LG

f----0 )( OL X LG O IllTABLE E

COL B

I• 227A OR 8 ~ 2 2 7 A OR B-- . j

COL D

TERM.

34

35

36

38

Fig. ~ V i s u a l Signals

Page 13



SECTION 518-410-300

11. PRESET CONFERENCE

11.01 A preset conference can be es tablished by

di aling a code or by the u se of a s ignal

key.

11.02 Afte r line seizure has been accomplished,

as describe d in 3, a ground is connected

to the preset conference circuit under control of

the selector circuit i f the dial was used or under

control of an operated s ignal key. This ground

will cause the operation of relay ROJ, un der control

of either the PC J or PC2 re lay . In operating,

the ROJ relay co nnects battery to the PC J and

PC2 relays and locks up under their control .

11.03 The PC l or PC2 relay will now operate .

Th e operation of the PCl or PC2 relay will:

(a) lockup, (b) release the RO l re lay, and (c) connect

audible signal powe r to a maximum of six on-premise

station audible signals. When off-premise station s

(m a x imu m of three) are to be included in the

preset conference, they must be connected to

punchings 1, 2, or 3 of the PCl re lay. When th e

PCJ relay operates as described above, a groun dis supplied to operate the lo ng line circuit.

11.04 When the dial is used, the T relay in the

selector circuit releases at the en d of th e

nominal1-1/2 second interval. The release of relay

T releases th e PCl or PC2 re lay, as th e case m ay

be , thus openin g the au dible s ignal path to the

called stations. With the us e of a signal key, th e

au dible s ignal at the called stations will operate

as long as the key is depressed.

SEQUENCE CHART

Page 14

COMPLETION OF

PULSE TRAIN (SEE FIG . 2)

SIGNAL

KEY ROTARY

SEE F IG .IO \

~ ® t225A)

AUO SIGOFF-PREM

STATION

SIGNAL

KEY

AUO SIG ®+OFF-PREMSTATION

R

(225Al

ROI

PCIOR

PC2

AUO SIG

ON-PREMSTATIONS

AU O SIGON-PREM

STATIONS

MAGNET

1-1/2 SEC

T

RELEASE

MAGNET

SELECTOR

SWITCH

OFF-NORMAL

CONTACTS

RELEASEMAGNET

(



SIGNALKEY

ROI

CONT ABOVE

COMPL ET ION OF PULSE TR AIN (SEE F IG. 2)

ROTARYMAGNET

26V(B )

OPE RAT IONAL SK ETC H

OPERATE PATH ROI RELAY ~ ! B l 1 1® ROI

j t -- 1ST 216A --t t+l•-- 2ND 216A--+-----3RD 216A---.-I .j.lt-217A

B

I)

TSB

SIGNALB KEY

>--<

SEE TABLE F

PC I ROI

- - - - 2078 OR C -- --- --.-. jo i----2 17 A OR 8-----1

R OI

CONT FROM BE LOW

PC IOR

PC2

CON T ABOVE

2 6 V( B )

2 6 V( 8 )

OPERATE PATH PCI OR PC2 REL AY

26Vf----,

0.

( 8) 1

2 9 l - - - * '

f- -- I ST 216 A ... -- 2ND 216 A -- •f4•>-- --- 3 RO 2 16A --- -<•+ • 17.4-0R-a-1

•I

SIGNALK EY ~

I !

PC I

.------ -- 2 07 8 OR C OR 8 -----1

L OC KUP PATH PCI OR PC2 REL A YAFTER RE L AY RO I RE LE ASES

f---•sT 216A 2N D 216 A t l• 3RD 2 16A ----<•* • 2 1 AO B-. j

SIGNAL

B KEY~>----<

..-..--- -- -- 207 8 OR C - - - - - ~ 2 1 7 A OR a-- J

CONT FROM BELOW

~ .._ __ ,

R( 225A)

A UO SIG ON- PR EMSTATION

SI GNA L

K EY

®R

( 22 5 A )

AUD S IGOFF-PREM S TAT I ON

®

AUD S I GON - PREMSTATIONS

PC IORPC2

AUD SPOWESUPPL

AUO S

POWERSUPPL

I - 1 2S

T

RE L EAMAG NE

SE L E

SW I T

OFF -

CON T

RELE

MAG N



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12. ADD-ON CONFERENCING

12.01 The incoming central office or PBX lin

picked up un der control o f an associ

key telephone system or key equipment line cir

When i t is ascertained that one of th e 6A st at

is to be conferenced with this call, a hold is pl

on the central office or PBX line.

12. 02 Th e 6A station to be conferenced is selec

signaled, and a talk ing path establishe

previously described.

12.03 The operation of th e add-on signal ke

the control station causes the operatio

relay N. The N relay in operating: (a) locks

under control of th e selector circuit, (b) opens

operate path of any other N relay, thus preventhe intercon nection of tw o or more outside l

(see inset on operational sketch), and (c) brid

the incoming central office or PBX line an d

6A st ation through the 120 F repea t coil.

12.04 The add-on conference con trol circu

eq uipped with A lead control.

If n add-o n signal key i s acciden

operated, stations busy on th e 6A

will be conferenced with th e cen

office or PBX in e .



SECTION 518-410-300

14. OFF-PREMISE STATION, INCOMING CALL

14.01 When an off-premise station is selected in

th e usual manner (by us e of dial or signal

key ), the C or S lead ground causes operation of

relay R in the long line circuit. The R relay: (a)

opens the transmission path between the off-premiseand local s ta t ions and (b) connects generator to

th e off-prem ise station 's T an d R leads operating

the audible signal .

Page 20

14.02 An off-premise station which is included in

a preset co nference arrangement has it s

lo ng line circu i t opera ted by a ground provided

from the operated PCJ relay in the preset conference

circuit.

14.03The

Rre lay will re

lease under control of

the slow release T re lay in the selector

circuit, or upon release of the signal key, re-establish ing

the transmission pat h of the off-prem ise station.

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c

SIGNALKEY

SIG

KEY

SEQUENCE CHARTSIINAL KEY COMPLETION OF (SEE FIG 21

PULSE TRAIN •

SIGKEY P ~ ~ = : T ( ~ ~ : . A

GALL 7)

*PG I

]--I:"'lsiGPRESET

GONF CALL

+Pel

ROTARYMAGNET

1-1/2 SEC

T

RELEASEMAGNET

ISS 3, SECTION 518-410-300

C ~ ~ ~ ' s ~ T ~ ~ ~ ~ ~ F (SEE FIG. 2)

SIGKEY f:UD

rSIG

SELECTORSWITCH

R

AUDSIG

A

ROT.MAG

26 V

(B )

RINGINGPOWERSUPPLY

1-112 SEC

T

SELECTORSWITCH

OFF-NORMALCONTACTS

RELEASE

MAGNET

OFF-NORMALCONTACTS

RELEASEMAGNET

OPERATIONAL SKETCH

OPERATE PATH R RELAY

TR

1---- 1ST 216A-+- 2ND 216A - -e+o t - - - -3RD 216A ----..j

B SIG KEY

•IISG X s

B @ 35,36 , PCI 1,2 ® 1• 1 1 - - + ~

R

.....___ 25 A ----j

OR 37 1,2,0R 4 OR3

f---217A OR B---1 @) I--- 225A ~TS 1ST BANKB C T OF SEL TABLE F

sw

1--- - -2078 R ( ; - - - - ~

OPERATE PATH

~ - - - 2 2 5 A - - ~ ~ . . . - - - - - - 225A - - - - - - t

TAIL£ F

2 0 1 1 . C ITll

LEAD T!IIMIIIAL

c 21

c ,.c 4At ,.c ..c 71

c ••c 91

c 101

Fig. 1G-Off-Premise Station, Incoming Call

Page 21



SECTION 518-410-300

15. OFF-PREMISE STATION, ANSWERING INCOMING

CALL

15.01 W hen an of f-p rem is e st at ion picks up in

re sp on se to an audible signa l, th e P re la y

wil l o pera te cau sing oper ation of relay C in the

lo ng line circuit . Re lay C in op erating op en s th e

au d ib le signal path for the off-pre m is e station.

Ta lki ng battery is su ppl ie d to th e ca lling s tation

fr om the A relay and to the of f-prem is e sta tion

from the Prelay.

SEQUENC E C H AR T

OFF -PREMIS E

STATION AN SW ER S

p

c

CAL LED AND CAL LING STATIONS C ONNECTE DTO T AND R LEADS

OP ER ATIONAL SKE TC H

OFF-PREMISE

STATIO N ANS WERS

p

c

CALLED AND

26 V(A )

26 V

!AI

PRIWINDING

'---- - - - ~SEC

WINDING

~ - - - 2 2 ~ A - - - -e l

I+-- 20 78 OR C -·----- 225A - - - - - 1 ~ - 2078 OR C ------1TALKING PATH

T

CA LL ING STi lTIONS OFF-PREM

CONNECTED TO TEL SET

T AND R LEAD S

Pag e 22

22 Pages

26V

(Al

A

II

PR I

WIN DING

SE CWINDING

CALLING STATIONTEL SET

t- ------- 22!:>A - - - - - - -eo !

T

TS&

- - - 2

Fig. 11-0H-Prem ise Station, Answing Incoming Call

26V

(Al

(

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518-410-300_i36a telephone system selector only arrangement

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