Patent GB-1046991-A (GB)
Title: Electrical apparatus for the retransmission of digital impulse trains
IPC: H04Q3/42
Filed: 1965-01-08
Abstract: 1,046,991. Automatic exchange systems. STANDARD TELEPHONES & CABLES Ltd. Jan. 8, 1965 [Jan. 10, 1964], No. 956/65. Heading H4K. A register sender for transmitting digits one at a time in the form of D.C. impulses comprises a first store in which each digit is registered, a counter which is incremented once per transmitted impulse and a control circuit which scans the store and counter once per impulse and in the event that it finds coincidence between the contents of the store and counter it stops impulse transmission and resets the store and counter to zero. The store is a magnetic core store and the counter is a binary counter which uses a chain of bi-stable circuits. The sender is applicable to a cross-bar system of the type described in Specification 960,960. General description of system.-A plurality of outgoing junctors have associated therewith a smaller plurality of magnetic core stores. When outward transmission of digits is required, the junctor seizes a store and causes the first digit to be recorded therein. The stores are electronically scanned and normally, data read-out is immediately rewritten. However, if during a scanning cycle (10 m/secs.), a control pulse (10 m/secs. long repeated once per 100 m/secs.) appears, then the presence of a waiting digit is detected whereby a central control circuit is called-in and scanning is stopped. Central control initiates an impulse sender, e.g. rotating cam giving 33<SP>1</SP>/3/66<SP>2</SP>/ 3  m/secs. break/make signal, and increments a bi-stable binary counter to " 1." The counter setting " 1 " is inserted into the core-store together with the original information read therefrom, central control releases and scanning restarts. Once per 100 m/secs., the store is read-out, the counter incremented by " 1 " and then the data is rewritten into the store. When central control detects coincidence between the contents of the store and counter, however, it stops impulse sending and clears the store. The next digit is inserted and the chain of events follows as before. Particular description.-A common read/ write circuit for a plurality of core stores is shown at RLE (Fig. 3). When the store is scanned, any "set" " cores therein produce output signals on wires fa, fb &c. whereby the associated bi-stable circuits ba, bb &c. are set to their " 1 " state. A timer DT provides time slots t0 to t4 in respect of each position of the scanner. Slot t0 is used for resetting the bi-stable circuits, t1 for reading-out of the stores, t2 for transmission to central control, t3 for reception from central control and t4 for rewriting into the stores or for addressing central control. In the last case, scanning is stopped and two cycles of DT are provided for the considered store. A cam call, which provides pulses of duration 10 m/secs. once every 100 m/secs., controls the setting of bistable circuit bk. Assuming that bk is set to its " 1 " state and the scanner is resting on a store which is waiting to initiate impulse transmission, i.e. core toa and some of cores tog to toj set, then at time t1, the set cores trigger bistable circuits ba and bg to bj. An AND gate responds to the conditions ba1 bk1 at t4 so as to signal central control CLC over wire fo and to inhibit the output of DT over bq. When central control is ready it triggers en over fp and releases DT via dq. Since the scanner has been stopped, the cores toa &c. are re-read at t1, and, at t2 the setting of ba is transmitted to ba<SP>1</SP> in CLC. bb and hence bb<SP>1</SP> are at " 0 " at this time since impulse sending has not yet started. At t3 the combination ba<SP>1</SP>1, bk<SP>1</SP>1, t3 ,  bb<SP>1</SP>0 opens an AND gate whereby a signal is transmitted over fr and fe to respectively set bl (Fig. 2) and bb (Fig. 3). The output on bl1 energizes transistor tr and hence brings up relay ra which connects the outgoing trunk to the impulse generating circuit GE. Relay rb which is controlled by cam CM2 initiates transmission of the first impulse. At t4 the settings of the bi-stable circuits ba &c. are transferred to the cores. At the next coincidence of a control pulse from CM1 and the scanner setting, cores toa &c. are once more read-out in order to set the circuits ba &c When CLC is seized this time, however, bb<SP>1</SP> is also set whereby a pulse appears on ff which sets the binary impulse counter bc to bf to " 1." Rewriting occurs as before but CLC remain connected. This third cycle of timer DT for a particular store is used for comparing the counted number of impulses-sent with the digit which is to be transmitted. If there is no coincidence, CLC releases. This continues until such time as there is coincidence, in which case, gates pd, pe, pf &c. (Fig. 4) all conduct and a stop-sending pulse is sent over fs to the junctor JT, i.e. bl is reset in order to release ra, and an erase pulse is sent over fg to the bi-stable circuits ba &c. Consequently at t4 no data is rewritten into the cores toa &c. and impulsesending in respect of the particular digit is complete.