Patent GB-503099-A (GB)
Title: Improvements in or relating to telephone systems
IPC: H04Q3/58
Filed: 1937-10-06
Abstract: 503,099. Semi - automatic exchange systems. AUTOMATIC TELEPHONE & ELECTRIC CO., Ltd., MoCLEW, J. W., and RICHARDS, I. T. Oct. 6, 1937, No. 27141. [Class 40(iv)] A calling subscriber on a tandem R.C.X. or a calling junction from an office more remote from the controlling office is connected to the operator via the finder of a finder-connector link preselected by an allotter associated with an idle junction and arranged to repeat digits subsequent to the first over the finder portion in the case of calls originated and terminating in the more remote office. Calls incoming from the direction of the control office are established over the same links. Specification 502,545 is referred to. In one of the systems described co-ordinate switches of the kind described in Specification 391,123 are used and in the other, uniselectors. Figs. 2, 3, 14 and 15 accompanied the Complete Specification and differ slightly from the corresponding figures accompanying the Provisional Specification. Call by local subscriber; co-ordinate call finder. Line relay R (which may be operated by a calling magneto or in the usual way) locks in series with common start relay AN which is followed by ST, and by JA, JB in the first idle junction circuit. The pro-selected link is seized by the application of ground to wire 25 over low resistance relay JRK which energizes JRT which locks up, energizes FS and replaces, JRK by RK. VR is then allowed to pull up and locks up, energizing FF in the link circuit. Driving and test circuits are thus completed for the vertical magnet FVM and vertical wiper FVW. Common test relay VT stops the switch on the marked level and its resistance is low enough to guard against double connections. VT energizes RS whereupon. FF falls and completes the rotary circuit. When the calling line is reached, the rotary magnet is held over the vertical wiper and wiper LF4 in series with FF which then connects the link through, locks in series with the cut-off relay K releases the rotary magnet and energizes Pin the common circuit. JRT is thus released and JSW locks up, connects the junction to the link, extends the start lead to the next idle junction circuit, and releases JA which releases JB. While JB is operated, ringing current is applied to the junction from a ringing and tone equipment resembling that described in Specification 503,761. Control of connector by operator in local call: On levels associated with ordinary lines, the finder -operates MS which provides the calling line with talking battery via FI. When the operator plugs in, A, B, BA pull up and if the calling party is still on the line and FI accordingly is energized, DD pulls up also and reverses the connections of relay A to signal the fact to the operator. In the absence of the signal the operator unbalances the junction to energize OC and cause RF to ring the line. The connector is then set on the calling line for checking purposes if desired and then on the wanted line. Relay A repeats the first digit to vertical magnet CVM in parallel with relay C which entergizes CA, and off-normal relay VN is operated at the first step. Clicks, in the calling party's receiver are prevented by a shunt round contact a2 put on by relay ID which was operated on the seizure of the link circuit. At the end of the digit, C, CA, ID, DD fall back and E, ER pull up. If the level dialled is one allotted to ordinary local lines, CR pulls up on the relapse of C, disconnects a<SP>8</SP> to guard against clicks in the calling party's receiver and directs the next digit to the rotary magnet via relay E. (lower). Rotary offnormal relay NQ is operated at the first step and at the end of the digit a temporary circuit is made over contacts of relays C, E which have different release times for test relay H. If the line is busy H remains inert and the relapse of E sends back busy tone. If it is idle H pulls up and rings it, first from a continuous and then, on the relapse of ER, from an interrupted source. When the called party replies F responds, locks up and completes the talking circuit over which the back bridge relay CI pulls up and energizes DD to signal the operator who then withdraws the plug. Relays A, BA, JSW, fall back but B is held by BB which is controlled by FI. On the relapse of JSW, the allotter moves on. When the calling party clears, the relapse of FI brings down BB, B, FS, FF and the switches are released. Call to neighbouring R.C.X. In this case HS is energized over the vertical wiper, HSR and F pull up and the rotary magnet interacts with busy relay BY until wiper CS3. encounters the battery connection of an idle junction. BY is then held and H, HA pull up releasing the magnet and BY. The outgoing junction is now looped via, CI, CD which are shunted during the repetition at a<SP>2</SP> of subsequent digits. The reply signal is taken up by CD which energizes DD to repeat it to the operator. Call to local party-line. In this case PR is energized as well as CR and the ring-trip relay F is energized prematurely and causes the operation of H if the party-line is idle to energize ED which looks up. A third digit is then repeated to code-selecting equipment (not shown) associated with. the line. During this digit RC is operated and at the end of the digit, ED, F, RC, C, CA, E, ER are released and the call is completed in the usual way. Reverting party-line calls. Terminals of party lines in the bank LF6 of the under are connected to corresponding terminals in the bank CS4 of the connector. A circuit is thus made for PRR when a reverting connection is required. PR, CR are operated also. BY is prevented from operating and H is energized on the relapse of C in spite of the busy condition. The extra digit is then dialled to the codeselecting device (not shown). Call from neighbouring R.C.X. The initial operations are the same as for calls originated locally, except that MS is 'not operated, but if the call is to terminate in the originating office, HS is short circuited by a connection from the left hand terminal in the connector vertical bank to ground at fs3 via bank LF6 of the finder. The connector therefore does not hunt and the next digit is repeated back over the finder wipers. The reply signal is in this case forwarded to DD by FD and when the operator clears, both junctions are released. Calls from coin boxes. A discriminating relay (not shown) associated with an additional finder bank may cause such calls to ring the operator via a half-wave rectifier. Calls from main office. When the operator plugs in, JC pulls up energizing JCR. JSW switches through to the allotted link, replacing JC. by A whereupon B, BA pull up and the connection is set up as previously described. Establishing checking connections and preferred calls. To cause the connector to switch through to a busy line the operator unbalances the junction to energize OC which is followed by RC, HR. This disconnects the finder side of the link and establishes a talking circuit over the connector wipers. In the case of calls from the neighbouring R.C.X., the operation of OC at the tandem office energizes RF which unbalances the junction to the neighbouring R.C.X. To break down the checking connection, the operator applies a high-voltage pulse to the junction in the direction to operate TO which energizes BR to release the connector. In the case of a call from the neighbouring R.C.X., SRA is energized also to pass the high voltage pulse back to that exchange. In the case of preferred calls the local parties are asked to hang up and when OC is released, RC falls and BP is energized and locks up to prepare the switching relay. The operator then re-operates OC, RC to ground the test wiper and so force release if one of the parties tries to hold on. On the relapse of OC, RC, the switching relay H initiates ringing and the call is established in the usual way. All links or junction circuits busy. A common relay RFB connected via isolating rectifiers to the release wires 25 of all the links falls back when all these are grounded and energizes ARB, RB. These arrange for the transmission of busy tone to calling subscribers and to the operator and prevent the allotters from hunting. If all junction circuits are busy, the starting ground is extended to ADB which gives a busy signal. Premature dialling. Dialling before the operation of JSW releases JC which energizes JBR. The latter locks up, sends back busy tone and opens the allotter hunting circuit. Battery charging. The R.C.X. battery is normally being charged via resistances from the main office battery. Testing arrangements; fault alarms. After setting up a connection to a.line to be tested, the test clerk operates TC by means of a highvoltage pulse of suitable polarity. This operates TS and, in the case of calls to the neighbouring R.C.X., SRB which passes the pulse on. At the end of the pulse SW is operated and a metallic connection free of transmission bridges is thus made to the line. Relay A is held meanwhile in a local circuit. TS, SW are released, to enable the line to be released, by a momentary re-operation of TC. To test the exchange equipment, a connector is set to a special test number to energize TN. If all is in order, the test clerk receives busytone over a double-wound retard TT when the connector switches through. If however a fuse has blown or a switch has stuck, off normal relay FA or relay Z causes inverted ringing tone to be given instead. The fuse alarm relay also lights a lamp and unless key KAC is operated, gives an audible alarm. A further lamp indicates that KAC has been operated. If a switch fails to return to normal, W which is included in all the homing circuits and starts interrupter relays 2R, 2RA is held long enough for relay Z to be energized through the action of a set of timing relays 2A, 2B, 2C. Z gives visible and audible alarms. Faulty action of finder. If a finder fails to start or to find the line a da