Patent GB-339784-A (GB)
Title: Improvements in or relating to telephone systems
IPC: H04Q3/00
Filed: 1929-12-05
Abstract: 339,784. Pollak, J. E., (Siemens & Halske Akt.-Ges.). Dec. 5, 1929. Automatic exchange systems.-The invention relates to working between exchanges of the revertive-control type and of the step-by-step type. When a call is initiated in the revertive-control exchange RCX, a junction Lv to the step-by-step exchange SSX is seized, and the incoming group selector IGW2 thereat acts as a discriminator in response to the first digit, which goes also to the register-controller Sp in the usual manner, effecting release of itself and the junction Lv in the case of a local call or causing the registercontroller Sp and the first group selector IGW to be dissociated from the connection in the case of an interexchange call. When a call is initiated in the step-by-step exchange SSX, the first group selector IGW1 responds to the first digit and, if the call is for the revertive-control exchange RCX, a junction Lr is seized over a relay group RX to which a register-controller TG is temporarily connected. The junctinns Lr terminate in ordinary first group selectors IGW at the exchange RCX, and the junctions leading to group selectors which have been dissociated from their call finders are taken into use in preference to the remainder. The register-controller TG records the remaining digits of the wanted number and repeats them to the register-controller Sp preceded by a fixed digit denoting the exchange RCX in order to keep uniform the number of digits dialled by subscribers on the exchange SSX. Call initiated in revertive-control exchange RCX. The call is extended over call-finders IAS, MAS to a first selector IGW, and a registercontroller Sp is taken in use in the usual manner, Relays An, R energize, and magnet Ddw advances the switch DW into engagement with an idle junction to the exchange SSX, and relays T1, C2 pull up. Line relays A2, B2 energize in the incoming group selector IGW2, and the first dialled digit is repeated by relay R at contact 7r to relay A2 and thence to the vertical magnet H2. Series relay V3 falls back at the end of the train, and if the digit denotes an inter-exchange call, rotary magnet D2 operates in search of an idle trunk. Relay F energizes and locks when the junction is seized, and relays V1, V2 energize at the first dialled impulse and fall back sluggishly in turn at the end of the train to operate relay X, which connects the calling loop directly to the junction and opens the connections to the first selector IGW and the register-controller Sp. The remaining digits are repeated by relay A2 to succeeding selectors at the exchange SSX to complete the connection. If the first digit denotes a local call, at the first rotary step of the incoming selector IGW2 a shaft contact mf2 is closed, shortcircuiting relay C2, which disconnects relay T1 to release the junction and the selector IGW2. No circuit is completed for relay X, but relay Y energizes and connects the calling loop independently of relay R to the first selector IGW at the exchange RCX. Call initiated in the step-by-step exchange SSX. The first selector IGW1 responds to the first dialled digit. and hunts for an idle trunk in the same way as' the selector IGW2 described above, extending the connection to the relay group shown in Fig. 3 if the call is for the exchange RCX. Relay C3 starts the switches Spwl, DW1, which take into use an idle register-controller TG and an idle junction to the exchange RCX. In the case of each dissociated selector IGW relay X energizes as described above, and connects up common relay G, which opens the test circuits Lcl of all the junctions at contact 50g, while the test circuits of all those leading to dissociated selectors are closed by the relays such as X at contact 47x, so that only those are selectable. Relay T3 upon operation connects up over wire Ld1 relay E, which opens the corresponding circuit of relay G. If therefore all the junctions leading to dissociated selectors are taken into use, all the parallel circuits of relay G are opened, and the remaining junctions leading to idle selectors are rendered selectable. The second and succeeding digits are repeated to relay Jan of the registercontroller, and when registration is complete, contact zg is opened, and the stored digits are sent out over the junction from contact izg via relays J1, A, preceded by a preliminary impulse train corresponding to the first digit.