Patent GB-256992-A (GB)
Title: Improvements relating to telephone systems
IPC: H04M3/60
Filed: 1926-08-16
Abstract: 256,992. Barnay, A. Aug. 17, 1925, [Convention date]. Void [Published under Sect. 91 of the Acts]. Automatic. and semi-automatic exchange systems.-A system is described in which local calls between subscribers on a rural exchange are set up by automatic switching apparatus at the rural exchange controlled from an operator's position at the main exchange. A rural exchange subscriber's line 5, 6, when put in a calling condition, is automatically connected over a common main exchange junction CC to a manual operator's position, means being provided for preventing the junction from being taken into use by a second party. If the wanted subscriber is a local one the operator takes into use a connecting circuit C2 at the rural exchange associated with an outgoing junction 42, over the lower leg of which she transmits first the calling party's number and then the number of the wanted subscriber. A calling connector on the left-hand side of the connecting circuit C2 and a called connector on the right-hand side, both of the general kind described in the parent Specification, are thereby set on the calling and wanted lines respectively, a single common marking switch 39, 52, 51 being successively used for tens and units marking in both connectors. The junction CC is released when the wanted connection is completed. Incoming calls from the main exchange are completed by a connector C1 set by impulses sent by the operator over the upper leg of the junction 42. An arrangement is provided for changing the rural exchange battery from the main exchange over the lower leg of the junction CC and both legs of the junction 42 in parallel, when neither of these junctions is in use. An alarm is given and the charging stopped if a fault develops on a line. Calls from rural exchange to manual exchange operator. When the subscriber at the rural exchange removes his receiver line, relay 1 energizes over the wire a and the calling loop 5, 6, locks to a local earth at armature 3, connects the calling line to the common outgoing junction CC, and energizes a switching relay 13. Relay 13 completes a series circuit over one leg of the junction for a relay 16 and a polarized relay 17 at the manual exchange, the direction of the current being such that both relays pull up. The relay 13 also energizes a switching relay 21, common to both junctions CC, 42, and extends the wire a to a self-interrupting relay 14, so that if another party calls, the relay 14 energizes in series with his line relay and gives a busy signal. Relay 16 energizes relay 22, and relay 17 energizes another common junction switching relay 23 and lights a calling lamp L1. The operator throws her calling key K1, energizing a relay 27, which locks up, closes an alternative circuit for relays 16, 17, and lights an engaged lamp L2 in place of the lamp L1. The operator can now converse with the calling party. Should the calling party, hang up, relays 1, 13 relapse, and the direction of the current is reversed over relay 17, which falls back and cuts out lamp L2. The operator then restores her key K1. Should the operator restore her key K1, relays 16, 17, 27 relapse, but before the relapse of relay 22, a circuit is closed for cut-off relay 35, which locks up, disconnects the calling line from the junction CC, and de-energizes relay 13. The relapse of relay 17 extinguishes the lamp L2 to give the operator a disconnect signal. Local rural calls. A rural party desiring to obtain connection with another party on the rural exchange, removes his receiver, and after becoming connected to the manual exchange operator as described in the preceding paragraph, states his number and the number of the wanted party. The operator throws her local connecting key K2, thereby closing a series circuit for polarized relay 37 and the line relav 36 of the local automatic connecting circuit C2, over the lower leg of the incoming junction 42 and the normal contacts engaged by wiper 40 of the calling side connector and by wiper 39 of the marking switch. The current direction is such that both relays 37, 36 pull up, the former lighting a supervisory lamp L3, and the latter energizing relay 44. The operator now throws a dialling key K3 to connect up her impulse transmitter D, and sends the number of the calling party. The first impulse series is sent to the magnet 47 of the marking switch, and to relay 50 which is rendered slow to release by being short-circuited during the subsequent responses of relay 36. The release relay 44 is also rendered slow-to-release in this manner. In the first three positions of the marking switch, a stop relay 62 is energzed over test wiper 59, and holds open the circuit of the stepping magnet 57 of the connector to give the marking switch a start. After the third position is passed however, relay 62 relapses and closes the circuit of the stepping magnet 57, which advances the connector wipers until the marked group of lines is engaged, upon which the relay 62 again energizes and opens the driving circuit. Relay 50 relapses at the end of the impulse series and when relay 62 pulls up, a relay 65 is energized and closes a restoring circuit 67, 68, 52, 69, 47 for the marking switch, which advances to an intermediate normal position. The second digit is now sent to set the marking switch, and the connector advances as before to the marked line in the selected group, whereupon the stopping relay 62 pulls up, and relay 65 closes the restoring circuit of the marking switch again. Relay 70 has meanwhile energized over wiper 52, locked up, and closed a circuit for relay 75, which also locks and transfers the marking switch control circuits to the called side connector. The operator now dials the number of the wanted party. and the called side connector is set on the wanted line under the control of the marking switch in the same manner as the calling side connector was set on the calling line, with the exception that the marking switch is not restored after the last digit. Busy test, signal, and release. If the wanted line is engaged, the test relay 80 is shunted by earth through a low resistance on the test contact, and the marking switch restoring relay 65 pulls up, and energizes a relav 82 which connects battery in place of earth to the lower end of the winding of relay 36, thereby reversing the current over relay 37 which relapses and cuts out the lamp L3. The operator releases the connection as described later by opening the circuit over relay 36. Ringing current; completion of connection. If the wanted line is free, test relay 80 pulls up, locks over its lower low-resistance winding thereby reducing the potential on the test wiper, and energizes a relay 87 to start the ringing apparatus, which supplies alternating current to the wanted line over a supervisory lamp L4 and the ring-cut-off relay 88. When the called party replies. the ring-cut-off relay 88 locks energized and completes the talking circuit. The calling party receives talking current over his line relay 1, and the called party over relay 82, which connects battery in place of earth to relay 36 to cause the relapse of the polarized relay 37 and the extinction of lamp L3. The operator then restores her calling key K1 releasing the calling line from the junction CC as previously described. Release. When the called party hangs up, relay 82 relapses and causes the response of relay 37, which again lights lamp L3. The operator restores the connecting key K2, thereby shortcircuiting relays 36, 37. The release relay 44 is now deenergized and closes restoring circuits for the marking switch and for the calling and called side connectors. Release by operator during conversation. This is effected by throwing a key K4 to open the circuit of relays 36, 37 and cause the relapse of the release relay 44. If the called party does not hang up, he is automatically connected to the operator's position over the junction CC in the manner previously described, and may then converse with the operator. Incoming calls to rural exchange. These are extended over the incoming junction 42 and an associated incoming connector C1 which is controlled by the operator in the same manner as the called side connector of the local connecting circuit C2, the impulses from the operator's dial D1 being sent however over the upper leg of the junction 42. The switching relay 21 is energized at this time over a rest contact of relay 16, which is short-circuited by relay 101. whilst the switching relay 23 is energized by relay 101, which is energized by a relay 102, the circuit of which is closed when the operator plugs into the answering jack J. Charging rural exchange battery from main exchange.. When no call is in progress. a series circuit exists for relays 16, 17 over the upper leg of the junction CC. Relay 17 is inert but relay 16 is pulled up, so that the switching relays 21. 23 are de-energized and the rural battery B1 is connected through a polarized relay 95 and a simplex circuit including the lower leg of the junction CC and both legs of the junction 42, to an ampere meter switch S and the main exchange battery B2. The polarized relay 95 is normally actuated and shunts its high-resistance lower winding, but if a fault earth develops on a junction line, the current is reversed and the relay 95 relapses and cuts in its high-resistance winding. At the main exchange the current increase through the ampere meter causes the switch S to close a circuit for relay 99 which opens the charging circuit and lights an alarm lamp L<5>. Specification 223.985 is referred to.