Patent GB-380046-A (GB)
Title: Improvements in or relating to automatic or semi-automatic telephone systems
IPC: H04Q3/62
Filed: 1931-05-28
Abstract: 380,046. Automatic exchange systems. STANDARD TELEPHONES & CABLES, Ltd., Connaught House, Aldwych, London. -(Deakin, G. ; 67, Broad Street, New York, U.S.A., and Hatton, W. ; 46, Avenue de Breteuil, Paris.) May 28, 1931, No. 15613. [Class 40 (iv).] In a P.B.X. in which local and outgoing calls are made automatically, but incoming calls are dealt with by an operator, the operator on going off duty throws keys individual to the incoming junctions for associating them with particular subscribers who are able to transfer incoming calls to any subscriber. If the special subscriber is busy, an incoming night call breaks down the local connection. Local calls are established by means of link circuits comprising a finder and a 3-digit final selector comprising two switches, the. final selector being marker-controlled as regards the hundreds and tens digits. Incoming junctions terminate in similar final selectors. The marker of the junction circuit is controlled to act as a timing set to give forced release if the attendant fails to answer an incoming call. Construction of switches. The link circuits are built up as standard units wired up internally, the external connections being led along a channel along the ends of the unit frames. The frames preferably comprise two portions hinged together so that they may be swung apart, one portion carrying the switches and the other the relays. Local call to single line. The calling line relay L, Fig. 3, energizes Ur which energizes the starting relays Ls, Fig. 1, of all idle links. The finders SMF then hunt under control of their relays Lt. When the line is found Lt, Pb pull up at once and Lb shortly afterwards to provide for double testing and switching relay E is operated in series with the calling cut-off relay and energizes line relay As, which holds Lb, and A, which releases Ls, Lt and Pb, energizes Hs and sends back dialling tone. The first digit steps SM which in a local call energizes Lt over wiper e of the marker and wipers el, e2 of the conversational switch, and when the series relay Lm falls, Ha is operated via wiper e. The marker SM then responds to the 2nd digit and as soon as it moves, Lt falls and SMS1 begins to chase the marker. If the digit is greater than 5, SMS2 is started and SMS1 stopped. The position to which the selector is stepped is determined by cross connections between the e banks of the selectors and the marker which provide circuits for the test relay Lt. At the end of the 2nd digit, Lm energizes Tc, which transfers the numerical stepping circuit so that the selector responds to the final digit directly. Lm on operation energizes Pb which energizes Rc. If the line is a single line, Pb falls on the relapse of Lm and releases Hs, a temporary test circuit being thus made over Ft. If the line is busy, Ft does not pull up and busy tone goes back from BT. If it is idle Ft switches the talking circuit back to the ringing current connected up by Rc. Rc is cut off by the back bridge relay Cs. Local call to multi-line group. If the 1st line is busy, ground is connected to its d terminal and Pb is thus held and a selfinterrupting circuit is made for the driving magnet of the selector. When an idle line or the last line of a group is reached Pb falls and busy tone or ringing current are sent as in the case of single lines. Incoming call accepted. In response to ringing current, J, Fig. 2, energizes Jx, Cb, and the junction lamp glows. Jx energizes Cl which locks and holds Cb after the relapse of J, Jx. The answering key AK energizes Al which releases Cb and energizes Fx, Jx the latter homing the marker. Fx is followed by Lb, Lx, and F pulls up over the loop. The operator now dials the wanted number and when the dial goes off-normal Jh pulls up putting a holding bridge across the junction and connecting the operator's loop to As which energizes S and repeats the digit to the marker which is operated and controls the selectors similarly to that in the local link. In this case however the 2nd selector is connected up by relays C, C1 Rc energizes Cn which releases S to home the marker and connects up ringing current If the call is accepted, the answering key is restored, releasing Jx and thus energizing Da which completes the wanted connection and cuts off the operator. Cl, Al fall back Incoming call declined and transferred. The operator breaks down the local con. nection by operating RE which releases Fx, Lb, Lx, &c, and then sets up a new local connection. Incoming call offered tc busy line. The key LIK is operated momentarily to energize Dt which disconnects the test relay Ft from the test wiper and energizes it. A speech circuit is thus made to the busy line. If the call is accepted, the answering key is restored to complete the connection, the connection in which the wanted subscriber is busy being broken down by the connection of ground to his c-wire by the relay Da and consequent shunting of E in the local link. No reply from wanted line. In this case the answering key may be restored to allow the operator to attend to other business. Jx is held. The junction lamp glows is parallel with Rc. If the subscriber does reply the junction is switched through to him, and the lamp goes out. Alternatively the operator may release the local connection and restore AK but hold the junction by means of the key HK. The distant operator may reoperate J to signal the P.B.X. operator. Outgoing call set up by subscriber. When a subscriber dials O, a circuit is made over wiper f of the marker for Sj, Fig. 3, which operates Sj1 or Sj2 to energize St in all the idle junctions allotted to the group of local links concerned. St operates C if the call is from the 2nd 50-line group. The junction circuit selectors then act as finders being stopped on the calling line by Jt which is operated in a circuit over wiper d1 and wiper d of the local link marker and energizes Pb which marks the circuit busy. Dt also is energized (sluggishly to guard against double test) and energizes Tc, Ft. Ft energizes Da to extend the subscriber to the main office whereupon F energizes Fx which locks and energizes Lb which energizes Lx. On hearing dialling tone, the subscriber sets up his call in the usual way. The first relapse of F releases Fx which energizes Jx. Jx homes the marker, prevents operation of Cn over wiper band energizes Cl. When the marker gets home, Fx is energized again and Jx is released. If all junctions are busy, Bj, Fig. 3, sends back busy tone. Otherwise Bj remains short-circuited over the wire L and front contacts (not shown) of relays St. Outgoing call set up by operator. The operator throws JBB which lights busy lamps for all the busy junctions and then throws AK in an idle one to get connection to the main office. She then operates a dialling key (not shown) which prevents the operation of Jh when the dial is off-normal and dials into the junction. She then extends the connection obtained in the same way as an incoming call. Transferring established connection. The subscriber dials 1 (or operates a special push to produce a similar effect) momentarily releasing F to unlock Fx and Cn having been operated (after dialling on an incoming call and by the time pulse in an outgoing call), Cb is energized in parallel with Lb when F pulls up again and lights the junction lamp. When AK is thrown, Al is re-energized and energizes Jh and Jx which energizes Cl. Cb, Da are released and the operator is connected to the P.B.X. subscriber, the junction being held. The operator can now transfer the call as if it were a new one. Call to attendant. If 9 is dialled, At, Fig. 1, pulls up, connects Lt to the e1 terminal of the conversational switch corresponding to the first attendant and makes a driving circuit for SMS1. When this line is reached Lt energizes Tc which energizes Pb. Pb energizes Rc releasing At which releases Lt. If the line is busy, Pb is held and the switch hunts as in the case of calls to P.B.X. lines. Night service. When the operator goes off duty, she throws the keys NSK of the junction, and when Cb operates on an incoming call over the junction shown, Ns extends the junction to a particular substation, breaking down an existing connection if necessary. When the substation answers the call, F, Nf pull up and also Fx, Lb, Lx. To transfer the call, the subscriber dials 1 unlocking Fx whereupon Jh pulls up and locks holding the junction and As is put under control of the subscriber's dial. S is held during dialling over a contact of NSK. When the wanted subscriber replie., the operating subscriber hangs up releasing Nf, Lb, Lx, Jx whereupon Da completes the connection. Outgoing calls are set up as during the day, the junction being to the night attendant on incoming calls. Faults. The operator's microphone is normally fed by local battery but, if this battery fails (lamp glows), a key is operated to connect the microphone to the a and b wires. Another lamp on the operator's desk glows if the main battery fuse blows. Timing arrangement. In the case of incoming calls, at the end of the ringing period, Jv, Jx fall back, Sa operates its left-hand contacts after 3 seconds and energizes Ip which energizes SM. Ip also energizes I which releases Sa so that after 100 milliseconds Ip falls releasing the magnet and unlocking I. If the reply of the attendant or the arrival of a further ringing pulse to energize Jx is delayed long enough for the marker to reach its 10th terminals, Cn is operated and releases Cl to restore the circuit to normal. In outgoing calls each dialled digit energizes Jx to restore the marker, the time pulse operating between digits. After the final digit, Cn is ultimately energized, releases Cl and makes it possible to bring in the attendant.