Patent GB-528457-A (GB)
Title: Improvements in or relating to telephone systems
IPC: H04M15/38
Filed: 1939-04-27
Abstract: 528,457. Automatic exchange systems. FIDES GES. FUR DIE VERWALTUNG UND VERWERTUNG VON GEWERBLICHEN SCHUTZRECHTEN. April 27, 1939, No. 12685. Convention date, April 28, 1938. [Class 40 (iv)] The subscribers of a telephone system are divided into two classes, those who normally set up a large number of high-valued connections and those who set up only a small number, the circuit arrangements being such that particulars of high-valued calls set up by the first class are automatically recorded and all calls set up by the second class are metered in normal manner. In Fig. 1, Tn1, Tn2 are two subscribers associated with a group selector GW through preselectors VW1, VW2, respectively. Repeaters UE are only connected to banks in the selector GW which are used in making a high-valued call. When a high-valued call is made by either subscriber, a repeater UE is seized and an A.C. signal is sent back to the subscriber by operation of post springs DK. Printing apparatus RE is connected only when the subscriber has a switching device E to' respond to the signal. Call from a subscriber entitled to' normal metering. When the receiver is raised at Tn1, a loop is completed and relay R1 operates to start the stepping magnet D1 of the preselector VW1. When an idle line is found, T1 operates and interrupts the circuit of the stepping magnet D1. T1 switches through, and A operates followed by C(i). During the first impulse train, A controls a stepping magnet (not shown) to step up the wipers of GW which then hunt in known manner for an idle line whereupon relay P operates and subsequent digits are repeated by A over the a wire. When the subscriber at Tn1 hangs up, A and C release, but P remains operated over P(iii) to hold the calling and called subscribers' lines. Metering potential is connected to the b wire at a subsequent device and Zr operates. The resistance Wi4 is short circuited by Zr and the current increase steps on the meter Z1 of the calling station. Relay P is finally restored and the connection is released. When Tn1 makes a high-valued call, the post springs DK are closed to apply A.C. to the c wire, which produces no effect in this case. When a free repeater is found, P operates through C1 in IE.. Further impulse trains are repeated by Al. When the called subscriber answers, battery is applied to the lower conductor and G operates, locks through G(ii) and is followed by X, Y. When the calling Subscriber hangs up, A and C release, but P holds over W which operates to release X, Y, but G(ii) is still held. Relay W signals in known manner the end of the conversation and the arrangements for determining and transmitting metering impulses are connected. The contact zk is closed for each impulse and Zr steps on the meter Z1. When the metering impulsing is complete, a metering discriminating relay S (not shown) operates and releases W and P(iii) to release the connection. Call by subscriber entitled to recording. Low valued calls by Tn2 are metered in normal  manner and a high-valued call proceeds as in the case of Tn1 until the release. When Tn2 hangs up, A and C release and application of A.C. through DK operates E in VW2. Relay E disconnects the calling party and locks through E(iii) and C operates again over C(ii), the circuit including increased battery and a glow discharge lamp Gl. During the short period in which C is released, W operates and subsequently Y and C1 alone in UE remain operated. The printing apparatus RE is connected to the a wire and thence to ground. The device for transmitting impulses identifying the calling station to the printer may consist of a continuously operated shaft at the exchange carrying a series of impulse cams each of which can transmit impulse trains corresponding to a particular subscriber. Cams U, S, I on the impulse sender associated with Tn2 operate the contacts 19u, 20u, 22so and 11i in the manner indicated in Fig. 2. Contact 22so is opened to start the operation, F operates, holds and prepares a circuit for transmission of impulses by the contact 11i. At the same time A operates to remove ground from the a wire to complete the preparations for sending impulses to RE. The cam I operates 11i to transmit the impulses and 20u, 19u are operated in succession along with 11i to release the connection. Metering impulses may be transmitted from time-zone repeater to the printing apparatus over a metering contact whilst the call number impulse trains are being transmitted. The called number and the date and time of the call may also be recorded. The same printing apparatus may be common to a number of repeaters.