Patent GB-815152-A (GB)
Title: Improvements in or relating to telephone exchanges having subscriber's lines with different privileges
IPC: H04Q3/00
Filed: 1956-02-10
Abstract: 815,152. Automatic exchange systems. TELEFONAKTIEBOLAGET L. M. ERICSSON. Feb. 10, 1956 [Feb. 17, 1955], No. 4327/56. Class 40 (4). A 100-line cross-bar exchange gives only a restricted service for junction. calls and for general calls using coded lamp signals. In a call to or from a line with special facilities, a marker marks a control wire individual to the line and enables a relay individual to the service required to start a test for the line marking and thereby to determine whether the particular service is available to the line. General arrangement. Under the control of a register REG and a marker in two sections MA, MB, a calling line L has access to a called line over a finder switch SV, a link N, a group selector GVN and a final selector LV. The group selector GVN also gives access to junctions F. An incoming call on a junction F is completed through group selector GVF and final selector LV. When the line relay LR pulls up, in a call from line L, the marker section MA receives a signal over leads U, T and extends the line through link N and register connector RS to pulse-relay RR2 in the register. Dialling tone is returned from source SU2 to the line L through a third winding of relay RR2. Relay RR2 repeats the two dialled digits to a relay set OR and if the call involves a junction, the digits 0, 0 are registered by operation of magnets S40, BR1 followed by S40, BR2. Magnet BR2 is followed by a connect relay KR1 and the digits are transferred to relays TR10, UR10 in the marker section MB. The register holding relay RR3 is de-energized when relay KR1 pulls up and the register releases after a delay during which further operations take place. The marker MA is prepared by a signal from contact 212 over leads m6, n2 and a slow timing relay MR1 is energized. In the meantime, test relay MR3 tests over lead t3 and contacts of TR10, UR10 for a free junction, to complete the call. If a junction is free MR3 pulls up before MR1 and the dialled number is marked in the register MA over contact 221 and marking wires E. If the call is not barred, marker MA controls group selector GVN to complete the connection in known manner. If the call is for a line A (No. 11) within the exchange, the relays TR1, UR1 register the number, and the line is tested by relay MR3 over contacts of TR1, UR1 and over test wire d1. When MR3 pulls up, the connection is completed over group selector GVN and final selector LV. Outgoing junction calls barred.-When the number 00 for a call to junction F is transferred to relays TR10,UR10 in marker section MB, a potential is applied to control wire g1 from contact 294 and leads m8, d1. Relay MR13 operates over lead g8 to connect the test relay MR12 to the control wires of lines to which junction traffic is barred. Relay MR12 has two oppositely wound sections which neutralize each other in the local circuit from contact 339. Relay MR12 pulls up over control wire g1 and signals marker section MA over lead g7, t2 to direct the group selector GVN to connect the calling line to tone source SU1. Incoming junction calls barred to line No. 11.- In response to a call over junction F, the marker section MA is seized over lead t4 and it selects a register. The register is connected to the junction by a register switch RS, magnets BN and S22 being operated. The number 11 is registered in REG and is transferred to relays TR1, UR1 in marker section MB. In this case relay MR11 is operated by the register switch RS over leads g6, m7 and connects the test relay MR12 to the control wires of lines to which incoming junction calls are barred. When MR3 tests line L (No. 11) over contacts of UR1, TR1 and over lead d1 to cut-off relay BR, lead g1 is marked and relay MR12 signals the marker section MA over leads g7, t2 to direct group selector'GVF to connect the junction to tone source SU1. General call for line No. 10, the line being free but not answered.-On receipt of dialling tone, the general call code 09 is dialled and is registered in REG. Relay RR7 responds only to this code over contacts K0, K19 but relapses when RR6 pulls up. The register is cleared and dialling tone is again returned to the calling line. The number 10 of the wanted line is dialled, registered and transferred as before to marker section MB. Relays TR1, UR10 pull up and holding relay RR3 falls back after a delay to release the register and the marker. During the delay, relay MR2 pulls up and is followed by relays MR4, MR9. Relay MR3 tests the line No. 10 over lead d4. If the line is free, leads d4, g4 are marked from contact 233 and group relays MR5, MR7 pull up to light the lamp combination L1, L2 allotted to line No. 10. Relays MR5, MR9 keep the lamps alight for a period determined by thermal contact TK.