Patent GB-526996-A (GB)
Title: Improvements in or relating to electrical transmission and/or distribution systems for musical and like programmes
IPC: H04H20/83
Filed: 1939-03-31
Abstract: 526,996. Distributting music &c. ERICSSON TELEPHONES, Ltd., and DRYSDALE, L. H. March 31, 1939, No. 10067. [Class 40 (iv)] In a system in which programmes are selectively applied to transmission lines connecting the receiving station to the distribution centre under the control of an operator at the distribution centre, who dials over a control line to set selectors at the receiving station, three lines A, B, C are provided, C being normally used for control, but in response to special dialled digits, either A or B may become'the control line and C a transmission line. Programme selection.-To connect a programme to line A, the operator throws dialling key DLK and dials 2 followed by the number of the programme. Impulses are repeated by relay A over line C to relay AA, and the first digit sets the switch CS. Relay SA pulls up when dialling relay CA falls back, and the selector AS, if off-normal, goes home, whereupon CA re-energizes as well as DA. The second digit sets the selector AS, and when key DLK is restored all the operated relays fall back, the relapse of SA connecting line A to the selected receiver and closing the power supply circuit if necessary. A programme is connected to line B in a similar way in response to the first digit 3, relays SB, DB being effective to direct the second digit to the selector BS. In these operations, the switch CS at the distribution centre is also set by the first digit, but without effect. Changing control line.-To interchange lines A, C, the operator dials 4 and then restores key DLK. The setting of the switch CS at the distribution centre results in the operation of NA, EB, whereupon the switch ES steps to its first off-normal position in which switching relay AF energizes. Similarly, the setting of CD at the receiving station results in the operation of PA, CB, and the switch DS steps to its first.off-normal position in which switching relay CF energizes. When the operator dials 4 again, ER, AR operate instead of EB, CB, and the switches ES, DS advance two steps to the next normal position and AF, CF fall back and restore lines A, C. The digit 5 serves to interchange lines B, C, the switches ES, DS moving to their second off-normal position to connect up AE, CE. These digits serve also to interchange A and B -as the control line. Supervision &c.-The operator may connect a programme to the control line by dialling O followed by the programme number. The operation of BB after the first digit permits the switch CD to be set by the second digit, the receivers being wired to the later contacts of its banks, and switch through being effected by the relapse of CA. The selectors AS, BS may be restored to normal by dialling 6, 7 respectively, homing circuits being completed by SA, SB. A splitting key RSK allows the apparatus at the distribution centre to be operated ihdependently of the receiving station. The operator may communicate with an attendant at the receiving station by means of a key RGK, which applies reversed battery to operate AB, ringing the bell in a set TS. Relay RA disconnects AA, AB during conversation. Relay CR may be operated by reversed battery from the receiving station to ring the bell DCB.