Patent GB-1027465-A (GB)
Title: Telecommunication exchange apparatus
Inventor: TRUEMAN ROY
IPC: H04Q11/04
Filed: 1963-08-27
Abstract: 1,027,465. Automatic exchange systems. ERICSSON TELEPHONES Ltd. Oct. 28, 1964 [Aug. 27, 1963], No. 33817/63. Heading H4K. A circuit for the supervision of metering and the connection of tones to a time division channel in a highway to which the supervisory circuit is devoted, is activated in the channel time by pulses circulating in a delay line storage arrangement with a frequency of circulation equal to the channel repetition rate, the holding conditions for the circuit being maintained during pulsing out by the register. Each channel pulse comprises a signal portion and a speech portion and the supervisory circuit can apply line splits to the forward and/or backward paths in the signal and/or speech portions of a channel. The supervisory circuit comprises circulating delay line stores ST1 to ST13 and associated logical circuitry. Control is exercised over sources of busy tone, number unobtainable tone, equipment engaged tone, and pay tone. Circuit functions are time shared and governed by cycles of group pulses (g), vernier pulses (v), sharing pulses (s), and block pulses (ba). Class of service.-Vernier and time sharing pulse combinations indicate class of service. The examples given are the Y party to a party line, for whom the combination v5, s9 injects a pulse into ST5, and an STD party for whom the combination v6, s1 puts a pulse in ST6. Receipt of answer signals.-For local calls a signal gated by v11 s1 registers a pulse in ST13 while for STD calls a signal gated by v11 of s1, s11, or s21, registers a pulse in ST8 as permitted by ST6. Answer signals are subjected to a persistance check which for a local call, in the next gating interval after ST13 was supplied with a pulse, puts a pulse in ST12 if the signal still persists. From this point metering is sanctioned. If ST12 already carries a pulse in this channel time a fault signal is generated. For STD calls the persistence of the answer signal causes a count of 7 in a parallel adder comprised by stores ST8 to ST11 before the answer is recognized and metering sanctioned. Metering.-Each metering pulse is given a persistence check as gated by one of the group pulses. As gated by other group pulses the subscriber's meter total is read out from a regular store, the total is read out of an overflow store if the facility is provided the subscriber, and the total increased by one is written into the stores. Withdrawal of the metering instruction depends on erasure of stores ST12 and ST13. Failure of ST12 to erase produces a fault signal and inhibits further metering. Failure of ST13 to erase produces a fault signal but erases over an alternative circuit. Local metering is governed by the circuit by counting off an initial batch of 11 metering rate pulses followed by batches of 10; the completion of each count sends a metering instruction. STD metering is effected by relaying a metering instruction for each meter pulse received. Each meter pulse is timed for validity by the counter of stores ST8 to ST11. If the signal disappears before a complete count the count is reversed and only advanced when the signal re-appears. If the meter pulse disappears and re-appears after the count sufficient to achieve validity has been reached, further meter instructions are inhibited until the meter pulse finally expires. Connection of tones.-Tones are connected on command of an originating register which forwards a tone control signal to the supervisory circuit. For number unobtainable tone a pulse is registered in ST3 and ST5 and ST6 are cleared with the effect that NU tone is put on the backward speech path. For busy tone pulses are written in ST3 and ST5 while ST6 is erased. For equipment engaged tone pulses are put in ST3 and ST6 while ST5 is erased. The tones have a duration of between 3 to 6 minutes depending on when they start in relation to 3 minute starting pulses; a count of two such pulses disconnecting the tone. Association with coin and fee check circuit.- The coin and fee check circuit (CFC) is the subject of Specification 1,027,464. Each supervisory circuit is associated with a CFC by means of a pulse in a cycle OSG. A free CFC returns an idle signal and when seized by the supervisory circuit sends an acknowledgement signal causing a pulse to be recorded in ST7. If all CFC's are busy ST3 and ST6 are given pulses to connect equipment engaged tone and effect forced release of the connection. The supervisory circuit discriminates between privately rented and public coin boxes and provides coin slot release and pay tone signals. In the event of an emergency call a connection can be set up regardless of whether a CFC is available or not, although if a CFC is available it is seized for use. Clearing down.-If the calling subscriber releases the forward hold signal is removed causing a pulse to be written in ST2 and ST1 to be erased. The speech path is thereby split in both directions and busy tone is connected to the backward path. A pulse is restored in ST1 and pulses of 743 ms. spacing are employed to time out the disconnection. If the forward hold pulse re-appears before a count of two timing pulses the clearing down procedure is abandoned and the supervisory circuit is restored. If, however, the timing pulses reach the required count a pulse is injected in ST3 to inhibit further metering and disregard any further appearance of the hold signal until the circuit has been cleared by writing a pulse in ST4 which removes the forward hold condition and then erases to release the backward hold whereupon the stores clear down. If the called subscriber releases a signal effects injection of a pulse in ST4 at the next occurring one of a train of 3 minute pulses. The next such pulse erases ST5 and ST6 and effects backward and forward line splits in the speech channel. Consequent removal of the forward hold signal erases ST1 and ST2 retaining a backward hold and connecting NU tone to the backward path. The next occurring 3 minute pulse writes in ST5 causing the calling line to be parked until eventually a pulse is put in ST7 and ST4 is erased to release the circuit. If the calling subscriber releases before the connection of NU tone then release reverts to calling party release. If the calling party releases during NU tone the ST4 is cleared and releases the circuit.