Manual / Guide
Subscribers' Uniselector Circuits (P.O. Telecommunications Educational Pamphlet, Telephones 3/2)
Post Office training pamphlet on uniselector operation and circuits — background for the PURPLE replica's stepping switches.
Manual / Guide
Post Office training pamphlet on uniselector operation and circuits — background for the PURPLE replica's stepping switches.
Telephones 3/2 Draft Series P.O. Telecommunications E�ucational Pamphlet SUBSCRIBERS' UNISELECTOR CIRCUITS CONTENTS Page Introduction l Operation of subscriber1s line circuit l Shared service working 6 Fig. 1 appended REFERENCES Educational PaTirphlets - Draft Series, Telephones 1/1 Introduction The uniselector is used. in the subscribers' line circuit to :provide a calling s ubscriber with access to a free 1st Selector. uniselector are two relays, Associated with each used to control the operation of the uniselector. Non-Director Exchange The uniselectors used for subscribers' line circuits in non-director exchanges em;iloyinc positive battcrJ meterinp. have four wipers in their assemblies, and the banks have four arcs. nep;ative, Three arcs, he.ve in divi dual contacts but the fourth c.rc, has two solid parts insulated from each other. the private, riositive and termed the hominr: arc, The hor.1inr; arc is used to return the uniselector wiper assembly to the normal :position at the end of each call. Director Exchange The uniselectors used for subscribers' line circuits in a director exchan;:e differ from those used in non-dir ector exchanges, since in director exchanges metering is effected by the a:::iplication of a negative be,ttery over between the subscribers' line cir cuit and the 1st Code Selector. the use of five arcs - positive, a fourth wire ·rhis en tails negative, private� Deter and hor.i nr-, the latter having the sarne function as the homing arc of the forlr-arc u niselector. In both types of exchange the uniselector banks have the contact arcs. These contacts are numbered 0 to 24. 25 contacts on each of 0 is the resting Contact or i10me contact on which the wipers stand when the uniselector is n ot in use. The remaining contacts of each uniselector are connected, corresponding contacts of other uniselectors, tori:ether with to the 1st Selectors. Operation of subscriber1s line circuit Positive Battery Metering i.e. Fig. l (appended) shows a subscriber's line circuit, on the home contact. l. (Copyright Reserved) the uniselector normal, Issue 2.1,, 7/70 (7/71) Telephones Wllen the subscriber removes the handset frorn. its cradle, the cracne sprinc:s in operating comple te the loop of the subscriber1 s line and close the circuit relay 1. 3/2 for The circuit is comrleted via:F.arth - contact K2 contact Kl ( Normal ) ( normal ) - subscriber's loop - 1 - battery. - relay Relay L operates. Contact 11 is designed to mal:e before ccntact 12. This avoids the possibility of prenature operation of relay l: during the initial orieration of L and also the incorrect switchine: of relay K to a bus;y outlet should the subscriber clear while the uniselector is huntin[. Contact Ll pre:pares the circuit for the operation of the drivinc mafnet Dll, at the same time f'lacin� a sl"'iort circuit across relay -�.·�. Cont£�ct 12 pl11ces a busying eartli on the final selector multiple private to :;:irevent intrusion hy i ncoming calls anr1 comriletes the circuit for the operation of the driving magnet DJ\1 thus:- ( operated ) - hone co11tact of T,ri vate arc 11 ( operated ) - contact K5 ( normal ) sprinr: DM dm ( normal ) - magnet DM - battery. Earth - contact 12 private wiper - contact llagnet DE 01!erates. When the driving .mar.net is full�r operated its circuit is bro�'>:en at the inter rupter s:pring DM dm. r.s the uniselector mr-�chenisrn. is of the reverse action type, the wipers do not move until the drivinc; magnet releases. circuit is ln·oken, \711en the drivinr; magnet the arwature is returned to normal and the pawl engar:es with the teeth of the ratchet wheel, movinr'.: the wipers to the first contact. The earth from the homing arc ( DMl ) now takes over the busying of the final selector multiple after the uniselector wipers have moved from the first contac Z . On DM2 arc, ensaged outlets are marked by an earth whilst the absence o f earth marks a free condition. If an e2,rth is encountered by the private wipers, the driving magnet circuit is again completed. Earth on bank contact - :private wiper - contact contact K5 ( normal ) - spring DM dm The driving magnet DM o:;;erates again. ( normal ) 11 ( operated ) - magnet - rnr - batter y. When it is fully operated the interrupter sprinp;s operate and break the circuit to the drivin1; magnet which releases a.nd steps the wipers to the next contact. This process is re31eated each time an earth is encountered on the private bant contact, and. continues until a disconnected, i.e. free, contact is reached when the drivine; mar:n et does not re-operate. During the hunting by the uniselector for a bank contact crithout an earth on it, the earth extended to relay K by contact 12, contact and other en�raged private contacts, place and the earth on the home a short-circuit across relay K and prevent its operation. 2. (7/71) Tele.:phones 3/2 When the free contact is reached the short-circuit is removed from relay K, which operates over the following circuit:Earth - contact 12 spring DM dm At contact Kl, (operated) - relay K - (normal) - magnet DM - battery. the subscriber's ne8ative line is connected to the negative wiper and the circuit for 1 relay is bro}�en. At contact K2, the subscriber's positive line is connected to the positive wiper and the operating earth for L relay is disconnected. At contact K3, t�e holding circuit of relay K is prepared. At contact K5, the operating circuit to the drive map:net is broken. When tbe subscriber's loop is extended via the uniselector wipers and bank contacts to the first selector, the seizure of this selector causes be connected to the private wire. an earth to This earth is extended back to complete the holdint; circuit for relay K. Earth on private wire from 1st selector - arc contact DM2 wiper DM2 - contact K3 (operated) magnet DM - - relay K - spring DM dm - battery. The driving macnet does not operate in series with relay K because of the high resistance of this relay. Rel ay 1 is both slow to operate and slow to release. The release lag ensures that the holding earth for relay K is not disconnected at contact 12 before the earth from the private wire holds relay K. The operate lag allows the relay to be substantially fluxed before t>c uniselector commences huntinis; always obtained, contact. this ensures that the full slow release time is and is important should the uniselector switch to an early choice When relay 1 releases, contact Ll prepares the homing circuit to restore the uniselector to the home position at the termination of the call. disconnects the earth from the K relay, the private wire), Contact 12 (which is held operated to the earth on and also from the home contact of arc rn:l. While the uniselector wipers are off normal, wipers Dl!ll connect tl1e two sides of this arc together to rrerare the ho111inc circuit. 'The subscriber at this sta'.''.e receives dial tone (from the 1st selector) and corrpletes the call by diallinc the number of the cal.led subscriber. When the called subscriber answers, the operation of relays in the final selector applies a 50V positive battery pulse to the r:>rivate wire to operate the calling subscriber's meter. '.I'he metering circuit, is as follows. Positive battery on private wire - arc DM2 - private wiper tar� M tPG :u met er - rcct ifier - - - contact K4 (operated) - earth. 'r11e subscriber's neter operates only to a positive battery pulse because the rectifier offers a high resistance to current fron a negative battery. 3. (7/71) Telephones When the calline:; subscriber clears by re placing the hand::«:�t c�. its crc:,r:'le, the loor is disconnected fror.: the line and the :!:'inal selector relo:JS releas:?, guardinr; and holding earth is disconnected from the :private uire, 3/2 'J.Le disconnect:'..rY the holding circuit of relay K in the subscriber's line circuit and allowin, rela�r K to release. Contacts Kl and K2 restore to normal in pre:oo.ration for t:1e next call nad.e by the subscriber. Contact K3 disconnects the circuit between the private wire and reley K to prevent relay K or:ieratinf to an earth on any private contact during the subc;ecuent rotation of the wipers. Contact Klf disconnects t�1e metering circi.;.it to ,rzuard ai:::ainst operation of LL.e subscriber's meter by a positive battery pulse on a T>rivate contact durinr· :�ocin;: of the wipers. Contact K5 completes the drive mar:;net circuit. Arcs DFl are short-circuited by wiper rna.. A circuit for magnet DM is made thus:- Earth - arcs Dl>''.l - contact 11 contact K5 (normal) (norrrnl) - spring DE dm - magnet DM - battery. T�1e drive rnsnet rr:akes and hreaks its own circuit at sprinr DJ\� dri, the wipers ra;iica:r round until they rest on the home contact. earth on the hor1e contact of arc rnn, ste:ppin,':': As there is no the drive magnet is not energize(! when the wipers are in this position. T:ie suoscril>er' s line circuit ::i.s no'" ready to re-operate as described above �or the next call ori- i,i=ct<'/! 1!�• the subscriber. Incoming Call On a call inc011ing to the sub:;cril1er an earth is extended forward on the T.-lire from the final selector. battery which at rr'.'-�-· s 'P 1 c8-uses the operation of relay K to the DM contacts Kl and Y.:2 disconnect the L relay be.ttery and earth from the line to prevent tJ:1e final selector rinr:ing current being prenaturely tripped. 4. 'I'elephones 3/2 Fourth wi-re negative battery metering Fie. 2 shows a subscriber' :3 d.irectcr exchanp:e. unisel·�ctor circuit designed for use :Ln P. The circuit ancl operation are the so.tne 12.-; thht r1reviously clescrioea., with tl:e exception that the meter, >Lich is battery, rn:ie:rated by a ne,:ctive is connected to a se�:·an,te meter wire instead of the P wire. reason t�ere is no need for e rectifier as For thiG in the circuit considere� earlier. �1-... CONNEXION STRIP ON I. 0 F. CM4 - • • • -'=2 . +o +/\ K2 l l, DM3 • -:" • • • • • • • • p K3 • OM2 • p • • • • • LI K 1300 5 � 500 M -u--- ) M_. ����������- OM5 • F'ig. 2 5. "• • . . • • • Tvo-home-posi tion urr�se lector If the first choice i selector is faulty in the arrar, e�:�ents pre·viously light tr :,S fi c since eri.c> The new subscriber will seize t,·,e f<.:,ult:;' selector. stanG.a:rd line circuit overcomes this diffi culty b�r usini:;: a "sc.1i t" homins arc to :;:ive two hone positions for the uniselectors. 'i1!ie connexions of the horctin,i;-- c,rc and P arc of the two-hone-:Positim� subscriber's uniselectors are shown in Fiv. J. described, a subscriber will be isolated during :·eriod of call oric;inated b�i t he ·l �-..--0- •• • • • •• el2 p K.P!I!!�.. s 1300 OM IR34076IA � The operation is similar to that of the -.;revious circuit excer\� contacts 0 and 12 are wire cl as hor'.e contacts. C'n 11nisele ctor drives on to the next �lon:.c ;)osi ti on, rele2sc that fror.i a call�- the the hor::inr; circuit teiri.t r;,� de via ( nv rrml ) - r:5 conta ct ( normal ) - I".a'}'.net DE - battery. Earth - ho1,:ing arc - 11 contact SI.Jrin,:i; DM cm. Thus alternate calls durinrI a -:eriod of lipht traffic will se1ze different 1st selectors. Shared Service ,Jorki n;; Shared service workinc: is subscribers currents are transrr:.itted. exchan,;es a n:cthod of proviainr- telenbone service to two by neans of a com-10n p:;,ir of wires over which sic:nal1inr and speech Ori:�inally, shared a common line and she.red service sub:Jo·:�)<c;rs on automatic exchan:e eq_u:irment, but after a few years an additional facility of ser!arate net,,ri.n� :Por each subscriber was introdciced. circuit description of the exchange ec·'.uiy·c11t for both types of "'.::le ziven. 6. iTOrkin �: II will nov Telephones 3/2 Ccmmon metering In this system the following facilities are provided:- (a) OriGination of calls by either subscriber, in the normal manner, using one exchange calling equi�ment and a single meter. (b) Common metering, on the meter proper to the X subscriber's number, of all automaticall�r registered calls originated by both subscribers. (c) Allocation of a separate number to each subscriber, of incoming calls to either subscriber on an automatic basis, and the completion with selective rina-ing. There is no secrecy between two sharing subscribers. FINAL SELECTOR MULTIPLE TO SUBSCRIBER'S UNISELECTOR IR34077l A <\I --:_-:..-: __ � Fig. Fig. 4 4 shows the jumper connexions on the M.D.F. and I.D.F. vfoen originating a call, either subscriber extends a loop to operate relay L and the call proceeds in the normal manner. 7. Telepl:cones 3/? An incoming call to subscriber X results in :cinginr::; current flowing from the ne.,,.ative wire of the final selector multiple cable via the subscriber's B wire, be l and capacitor to earth. An incoming - call for subscriber Y results in ringin�<, l current flowing from the negative wire of the final selector multi:;:)le via the revet'sal jumper on the �i.D.F., subscriber's A wire, bell ancl capacitor to earth. Sepa,rate Metering The following facilities are provided:Either subscriber originates a call b�r depressing a callinc b utton on (a) :;i:� tele phone and lifting his handset. Each subscriber is a.llocated a separate calling eq_uipment, {b) separate meter and separate final selector number. Selective rinE".ing is e'.i ven on all incominr calls. ( c) There is no secrecy between the two sharinr: subscriber::;. Fig . 5 shows the jumper connexicJns on the H.D.F. and I.D.r'., tof):ether with the relevant circuit elements of the: line e�uipment for two sharinc: subscribers with separate metering. a call, The calling sie;nal received, is an earth on the from the Y or subscriber. A or B wires when eit;1er subscriber makes dependinp; on whether the call originateE> X subscriber respectively. Consider a call oririnating On aepression of the cnlliric button, an earth is fro:r.1 the Z R.prlied to the B wire to or:ierate relay 1 in the line equipment. Contact 11 prepares a circuit for the operation of the drivin� mafnet DM, the same time placint�� a Contact 12 at short-circuit across relay ::. completes the circuit for the o:i;:ieration of the driving map;net and at the sarn.e time places a busying earth on the final selector multiple private, thus preventing intrusion from incoming calls for both X and Y subscribers. This earth will also or:ierate relay K in the Y subscriber's line equipment c:md this relay r·emains held throu;--;hout the call. The X subscriber's uniselector then hunts and seizes a free 1st selector. The Y subscriber's uniselector will not move off normal. The X subscriber's meter is operated in the normal manner when +ve battery is received over the P wire. It is impossible for the conditions, since, Y subscriber's meter to be operated under these although K4 is closed, the P wiper has not r;1oved from normal to receive +ve battery. When the Y subscriber originates a call, he depresses the button on his telepi1one which extends an earth out on the A wire of the line. This earth completes a circuit for the operation of relay 1 in the Y subscriber's circuit. earth - subscriber's A wire, +ve wire on the M.D.F. The circuit for this is:and I.D.F., +ve wiper and home contact of the X subscriber's uniselector - Kl contact (Y subscriber1s line equipment) - relay 1 to battery. 12 cause the Y C ontacts 11 and subscriber's uniselector to hunt for and seize a free 1st selector, in an identical manner to that described when an X subscriber originates a call. The Y subscriber's meter is operated when the called subscriber answers (assu.'Yling the call to be directly dialled). 8. (7 /71) Telephones � 3/2 TO FINAL SELECTOR MULTIPLE �- M.O.F.- I 0 F �::: - � ----------<..-,__ _·__:� ' I A I I + ----------0 -:• Kl ·. • •• !,_ 2 -:r- + X SUBSCRIBER'S LINE EQUIPMENT K2 1 I -y-, I I---0-\I ,1 \� h I I '.I I I I I I I I I . t 6---<o-6-�---�p K3 (p 1)- . _ • • . . . LI � IJ>I 'IJ_ _L��. I . . K 5 K4 I I /b I I -:x:-- � - J _-GM>-------------� --- ·-�· ----· -.;-' --1 I I I I I I o----+---""'-...-----------1! 0---. --;.; o I I I 1 I l 0 }�·...• ..• • __.}� .: • •• I ,, -.:,_,,,_____-1.J p :4- O-------::i:___ _.__,,_2.._4 ___ I I I I l,P K ...:- El---��· �E ..•. K3 ?- 1 Y SUBSCAIBE.R $ LINE EQUIPMENT LI K 5 T ---0- -- - -<: M>---- --------- --� An incoming call for the X subscriber is received in the normal manner, i.e. ringing current is fed out over the -ve wire of the f inal selector multiple, via the B wire and the X subscriber's bell and capacitor to earth. Similarly, for an incominc; call to the Y subscriber, the rincing current is fed out over the -ve wire of the final selector multiple cable, reversal jumper on the M.D.F. to the A wire, throuc;h the and thence via the Y subsci·iber's bell and capacitor to earth. A description of the shared service apparatus installed at the subscriber's premises is given in Educational Pamphlet - Draft Series, END 9. Telephones 1/1. -/' CONNEXION • • • STRIP ON • 1.D.F. Kl � - - - - - - -,.-,.,.--:l0-------1..11111o. ..----------• :D M4 .. _ ,. I _ / ��-,ro· L -..--2 I ! . . T 1 + K2 - - - - -1- ---?J-----------, I �,. I, I 1 I I I I I I I I I I I I I ,, I I I I I I I I I I / l I I +} \ ----- DM3 .__ • . • • L2 • • p --4J-<..-u -- K3 • DM2 • : l • .,..._ • • • l"!"'!!'�!"ll K 1300 5 l '-v--' TO FINAL SELECTOR MULTIPLE OM 4 --r--- .. �� K4 M Fig. 1 (7 /71)