Patent GB-313682-A (GB)
Title: Telegraph concentrator
IPC: H04L12/04
Filed: 1928-04-03
Abstract: 313,682. Relay Automatic Telephone Co., Ltd., and Corner, A. C. April 3, 1928. Central-station apparatus.-Comprises a relay system whereby a number of service lines SA, SB, - - from control-office telegraph sets TA, SB, - - may be connected as required to lines selected from a larger number of outside lines LA, LB, . - the same switching apparatus being employed for connections originating in the central office as for those originating in outside offices. Outside line calling office line. The line magnets LEA, LEB, - - are normally energized via the contact LEA.1, the lines being normally earthed. A call is effected over the line LA, for instance, by breaking the line circuit, so that the magnet LEA releases, closing temporarily a circuit for the searching magnet LMA, from earth at OP.1 through LEA.3, BA.2, OA.4, LMA, to negative at RA.1. The magnet LMA thereupon closes permanently the circuits of the busying relay BA and connecting relay LAA via OP.1, LEA.3, 4, LMA.2, LAA, BA, LMA.5; it cuts off at LMA.3 all higher LM relays, and closes for itself a contact LMA.4 alternative to BA.2 which is now broken. The busying magnet BA lights the calling lamp CA via BA.1 and breaks BA.2 so that subsequent calls fail to energize I,MA but pass via LMA.3 to LMB. The magnet LAA connects the outside line LA to the office line SA at LAA.1, breaks LAA.5 so as to isolate the line LA from other connecting relays such as LAB, closes for itself at LAA.2 an earth contact alternative to LEA.3, 4, and re-energizes the line magnet LEA via LAA.4. The magnet LMA is consequently broken-circuit at LEA.3, but the magnets BA, LAA, LEA hold on throughout the message. If now a second line LB calls up by breaking circuit, the line magnet LEB releases, but cannot affect the searching magnet LMA which is brokencircuited at BA.2. The next searching magnet LMB therefore operates, connecting LB to SB by means of the connecting relay LB. Effect of call when all lines are busy. In this case the energizing circuits of all the searching- magnets LMA - - are broken at BA.2 - - , and when a call arrives over line LA, say, the consequent release of the line magnet LEA closes at LEA.3 : (a) The circuit from earth at OP.1 of a supervisor's lamp SLA; (b) A circuit giving a " busy " signal. This runs via ASB.6, CH2.2, CH1, so that CH1.1 closes the circuit of CH2. Thereupon CH2.2 breaks the circuit of CH1, and this action repeats itself, so that negative is intermittently applied to line via CH2.1 (intermittent) and LEA.2, the latter contact being closed so long as LEA is not energized; (c) A circuit for temporarily connecting to line the supervisor's instrument SI, in case the call should be a priority call, and for eventually breaking the circuits affected by the call. To this end the thermostat Tl is energized via ASB.6 so that after an interval ASB is energized, locking itself via ASB.5. Thereupon the instrument SI is connected to line at ASB.3, the busy-call magnets CH1, CH2 are cut off at ASB.5, negative is cut off from the line at ASB.2, and a further thermostat T2 is energized. After a delay (which gives an opportunity for receiving a priority call) T2 acts to close the circuit of ALB which re-energizes all the line magnets LEA of the calling line LA at ALB.1. Magnets ASB, ALB and lamp SL are thereupon restored to normal, but the line magnet LEA now finds earth via LEA.1 and line LA. Calling of outside line by office line. If the office instrument TA is to call the line LA, for instance, the key kA is depressed, energizing OA. The circuit of LM9 is thus completed from earth at OA.5 to negative at RA.1; the connecting magnet LAA thereupon acts to connect the required lines at LAA.1, while the busying magnet BA.2. acts to shield the magnet LMA from incoming calls by breaking BA.2, as the circuit of LAA and BA passes from negative at LMA.5 through BA, LAA, LMA.2, and wire MA to earth at kA. This circuit is locked up at LAA.5, the connecting magnets LAB - - are cut off from the line LA at LAA.5, and the preventing-magnet OP, energized at OA.3, cuts off earth at OP.1 so as to prevent energization of the searching magnets LMB - - pending the release of the key kA. Office terminals other than the one, TA, which is making the connection are warned off by the lighting of their lamps M via OA.3. Release of a line-connection. This is effected by the office telegraphist concerned by depression of his release key such as RA, which breaks the circuit of BA, LAA at BA.1. Supervision of telegraphists. So long as a key KA or RA is being depressed, negative is applied via RA.2 or OA.1 to a lamp SLA or SLB at the supervisor's table.