Patent GB-412616-A (GB)
Title: Improvements in telephone systems
IPC: H04Q1/40
Filed: 1932-12-31
Abstract: 412,616. Automatic exchange systems. TELEFONAKTIEBOLAGET L. M. ERICSSON, 33, Kungsgatan, Stockholm. Dec. 31, 1932, No. 37047. Convention date, Dec. 31, 1931. [Class 40 (iv).] Selectors and registers are operated separately and synchronously by locally-supplied impulses, control of the selector by the register being effected only at the beginning and end of each digit. In inter-exchange working, the control signals are relayed over long inter-exchange junctions as pulses of alternating current. The impulse-transmitting devices comprise oscillatory circuits controlling polarized relays. Detailed operation, Fig. 1. The test circuit of the call-finder AS includes a relay DR which connects the link FL to the common register REG. Relay IR energizing over the loop operates relay HR which locks relay DR and disconnects similar relays in other links. Three series of impulses are transmitted to registers RE1-RE3 over sequence switch SO1 which is advanced after each digit under the control of relay GR. When the first digit has been recorded, relay KR operates over the backcontact of GR and the upper bank of register RE1 and locks. Relay KR energizes impulse device SD1 which sends impulses to magnet RM1 and at the same time a loop is completed over link FL for relay MR which causes impulse device SD2 to send synchronous impulses to the vertical magnet GHM of the group selector GV. When the register RE has been advanced to normal, relays KR, MR, release, sequence switch S02 moves to its second position, and relay PR operates over off-normal contacts 26 to connect up rotary magnet GVM in series with interrupter SB1. When an idle final selector is found relays SR, XR, operate and control of the vertical and rotary magnets takes place in a similar manner to that for the vertical movement of the group selector, change-over relay TR operating when relay NR releases at the end of the tens digit. When sequence switches S01, S02 of the register are both in their fourth positions relay UR energizes and switches through the calling loop to feed-relay VR. If the called line is idle, relay YR operates to complete the connection but, if busy, relay NR remains connected up and busy current from buzzer SS is sent back. When the calling party hangs up, relays VR, UR, release, relays DR, ER, FR, operate momentarily, FR unlocking the cut-off relay BR. Inter-exchange working. When the group selector GV, Fig. 1, seizes a long-distance junction LL, Fig. 2, relays R2, R3, R4, R5, operate, R4 locking up and releasing R3 which in turn releases R5. During the operation of R5 a pulse of A.C. from source E is transmitted over the junction LL operating R6, R7, R8. At the end of the pulse, relay R9 operates and locks, connecting up relay XR in the final selector (similar to LV, Fig. 1). During each closure of the control loop by relay KR, relay R1 transmits A.C. from source E over the junction operating relays R6, R7, R8, and NR which controls the final selector as described above. At the end of conversation when relay R2 releases, interrupter SB3 is connected to relay R5 during the release period of relay R4 and at least two short pulses of A.C. are sent over the junction. After the first pulse whilst R7 is still up relay R10 operates and remains up for a short interval during the second pulse so that R9 is unlocked and the final selector releases. Impulse-transmitting arrangements. The impulse-senders SD1-SD3, Fig. 1, comprise a polarized relay PR1 in series with a condenser and shunted by a resistance M the relay controlling a contact BK which is oscillated at a constant frequency determined by the constants of the circuit. In another arrangement, Fig. 3, the oscillatory circuit is coupled to the polarized relay PR4 and to the circuit including the vibratory contact K by transformers T2, T1. In a third arrangement, Fig. 4, two oscillatory circuits are employed associated with separate windings PR5, PR6, of a polarized relay and the vibratory contact may be connected to the external apparatus through a further polarized relay PR7. Transformers may be inserted between windings PR5, PR6, and the oscillatory circuits. In a single exchange, a single common impulse-sender may be used for the register and selectors with suitable pick-up arrangements.