Patent GB-341045-A (GB)
Title: Improvements in or relating to switching arrangements for automatic and semi-automatic telephone systems
IPC: H04Q3/00
Filed: 1929-10-09
Abstract: 341,045. Automatic exchange systems. STANDARD TELEPHONES & CABLES, Ltd.. Columbia House, Aldwych, London.-(Stevens, C. E. and Schooneman, J. ; 81, Rue de Boudewyns, Antwerp, Belgium.) Oct. 9, 1929, No. 30625. [Class 40 (iv).] In a revertive control system in which the final selector moves to terminals marked by an auxiliary switch, which is set in accordance with both tens and units digits, the auxiliary switch sends back both sets of impulses from the same terminal bank, makes the same number of steps per impulse for both impulse trains, does not return to a home position between the digits, and has its terminal bank so interconnected with the final selector terminal bank that if the auxiliary switch makes a maximum number of steps, the final selector makes a minimum number and vice versa. The invention is described as applied to a system such as that in Specification 318,945, [Class 40 (iv), Telephones &c.], in which common control circuits are used and in which the final selectors comprise 51 point single motion switches with two sets of wipers at 180 wiping over separate terminal banks. Before the numerical operations of the control switch are commenced, the switch hunts for the final selector being used and enables it to connect itself with the control unit. Normal operation. When the final selector switch is seized Acr energizes followed by Ecr, and PC steps the control switch in search of the selected final selector. The operation of Ecr marks the control circuit as busy. Off-normal springs ON make when the switch moves, and when the brush i encounters the selected circuit Bcr energizes, stopping the switch and energizing Fr1 followed by Fr4 and Fcr. Relay Fr1 connects Dcr to the register controller (not shown). Relay Dcr recompletes the circuit of PC to drive the control switch and each time g passes an earthed contact an impulse is transmitted back over wire B to the register controller. When the tens register is counted out Dcr releases and Gcr energizes enabling PF to step the final selector in search of the line marked by brush f. When wiper e reaches the marked terminal Hcr energizes breaking the circuit of PF and energizing Lcr. Meanwhile the fundamental circuit has been re-established and Dcr re-energized. Relay Ycr, previously shorted by Dcr, now pulls up and Icr and Jcr energize. If Lcr has already operated the circuit for PC is recompleted and the switch again moves, brush g sending back revertive impulses as before. When the units digit has been counted out, Dcr falls away and Mcr pulls up, connecting Hcr to brushes h and i to mark the selected contact. When Mcr energized, Hcr and Lcr released, enabling PF to step the selector until e finds the marked terminal when Hcr re-operates followed by Lcr. Slowoperating relay Pcr energizes disconnecting Hcr from h and i and connecting it to d for P.B.X. hunting as described below. The called line is tested and the control circuit released as described in Specification 318,945, [Class 40 (iv), Telephones &c.]. P.B.X. arrangements. If the line called is a line, other than the last, of a P.B.X. group, the terminal in bank d is connected to earth via normal contacts of the cut-off relay Cor. If this relay is energized the earth is removed and when Pcr energizes, Hcr releases and PF steps the selector on to the next terminals. The lines are thus tested until a free line, or the last line of a group, is reached when the switch stops and operates as for a single line subscriber. The hunting facility of the switch is removed by throwing key NPBK. Connections between auxiliary and selector switch banks. These connections, which are shown in Fig. 3, are such that the revertive impulses are complementary to a base of 11. The wiring is so arranged that when the control switch makes a maximum number of steps the selector moves a minimum number and vice versa.