Patent GB-850361-A (GB)
Title: Improvements relating to automatic exchange systems
Inventor: FLOOD JOHN EDWARD
IPC: H04M15/04
Filed: 1955-12-09
Abstract: 850,361. Automatic exchange systems. SIEMENS EDISON SWAN Ltd. Dec. 7, 1956 [Dec. 9, 1955], No.35454/55. Class 40 (4). Information indicative of the charge for a call is registered in a first binary form on a magnetic drum and is then changed to a second binary form which is written into the same storage spaces on the magnetic drum as the first binary form and at a time when the first binary form is being read. The combination of two decimal digits dialled by a subscriber determines whether the call carries an initial charge independent of the duration of the call, is metered at intervals throughout the call, or is free. The magnetic drum is synchronized with a time-division-multiplex system and is common to the supervisory relay sets of an exchange. Each relay set receives two digits to register the fee before it receives digits to set up the call. Each relay set is allocated two storage compartments on the magnetic drum, one compartment passing under a writing head while the other is diametrically opposite and passes under a reading head. Each storage compartment comprises sixteen storage spaces corresponding to time periods tl to t16 marked off by the timedivision-multiplex system which also marks off a control period to at the beginning of each channel time to reset a number of bi-stable circuits. The magnetic drum is not shown but read 0 and read 1 wires 13, and 14, and write 0 and write 1 wires 7 and 8 are shown in Fig. 1C, interconnected such that normally a 0 or 1 read from storage space of one compartment is written in the corresponding storage space of the other compartment. The four gates G24 to G27 have a control wire 11 which, when energized, switches the read 1 channel to the write 0 channel, and the read 0 to the write 1 channel thus registering the complement of what is read. A subtraction circuit SC has a control wire 25 which when energized inhibits gates G40, G41, and opens gates G42, G43, so that a signal intended for the write head is diverted to the write 1 head whereas the first signal intended for the write 1 head is diverted to the write 0 head and operates a circuit E2 which, on the cessation of the signal applied to it, triggers the bi-stable circuit T10 to inhibit the input gate G39 and prevent further alteration of the binary input. Gates G2 and G3 with control wires 19 and 20 cause 0 to be written if wire 19 is energized and 1 to be written if wire 20 is energized. Registration of metering information in first binary form.-While the illustrated supervisory relay set is idle and during the appropriate channel times, a gate G1, Fig. 1C, transmits pulses at times t1 to t16 which over G2 write 1 in every storage space allocated to the relay set. When taken into use relays A and B operate. A contact of B energizes forward hold multiplex MX6 which during the channel period produces pulses on highway 35 disconnecting G1 for the remainder of the call. A contact of relay A causes impulsing multiplex MX3 to produce pulses on highway 33 inhibiting a gate G45, Fig. 1C, and opening a gate G4 to write 0 in each storage space t1. Relay A repeats the first impulse train during which relay C holds up. A contact of C energizes multiplex MX4 to produce pulses on highway 34 and by opening gate G5 and inhibiting gate G46 writes 0 in each storage space t2. At the first break impulse A falls back and the output on highway 33 ceases so that over G45 1 is written in a storage space t1 in one storage compartment while 0 is read in the space t1 in the other compartment. In this channel time there is no 0 read at times t3 and t4 so that, of the bi-stable circuits T1, T2, T3, in a receiving circuit RC, Fig. 1B, circuit T1 is operated over a gate G8 to provide an input to a gate G14 for the remainder of the channel time. With G14 stimulated, pulses are applied to control wire 25 of the subtraction circuit at times t5 to t8 to subtract 1 from the word stored in the spaces t5 to t8. At the end of the first break impulse output reappears on highway 33 writing 0 in the storage spaces t 1. At the second break impulse 1 is written in one space t1 by output on highway 33 at the same time as 0 is read in the other space t1. As happened in response to the first impulse, the second impulse causes the subtraction of 1 from the word stored in spaces t5 to t8. At the end of the first impulse train the storage spaces t5 to t8 register the complement to 1111 of the number of impulses in the train. At the end of the train relay C falls back to cancel the output on highway 34 of multiplex MX4, causing 1 to be written in one storage space t2 while 0 is read in the other space t2. Gate G7 in circuit RC is thereby operated at time t2 and triggers bistable circuit T2, opening gate G11 to write 0 in the storage spaces t3. Each break impulse of the second impulse train causes 1 to be written in one storage space t1 while 0 is read in the other space t1 so that G8 is opened and bi-stable circuit T1 is triggered. As O is now read in the spaces t3, gate G6 is opened to trigger bi-stable circuit T3, the output of which inhibits G14 and opens G13. At times t9 to t12, therefore, pulses are applied to the subtracting circuit SC during each impulse. The storage spaces t9 to t12 thereby store the complement to 1111 of the number of pulses in the second impulse train. At the end of the second train relay C falls back, cancelling the output on highway 34 and causing 1 to be written in one storage space t2 while 0 is read in the other space t2. Gate G7 in circuit RC opens to trigger bi-stable circuit T2. As 0 is read in storage space t3, gate G6 is opened and triggers bi-stable circuit T3. With both T2 and T3 triggered gate G10 is opened at time t4 with the following consequences. Over gate G12 0 is written in the storage spaces t4. Over input highway 36 of switching multiplex MX5 and pulse lengthener L1, relay N is operated and locked up for the remainder of the call to disconnect multiplex channels MX3, MX4, and to extend the line forward for further dialling. Over lead 42 a bi-stable circuit T4 in a translating circuit TC is triggered. Registration of metering information in the second binary form.-The pulse applied at time t4 to the translating circuit TC initiates the following changes in the binary numbers registered on the magnetic drum. The number stored in spaces t5 to t8 is changed to its complement with respect to 1111, 1 is then subtracted and if the first metering train has 1 to 8 impulses the eights digit, if 0, is changed to 1, while if the first metering train has ten impulses the eights digit, if 1, is changed to 0. The number stored in spaces t9 to t12 is changed to its complement with respect to 1111 and if the first train has 1 to 8 or 10 impulses the eights digit, if 1, is changed to 0; while if the first train has 9 impulses the eights digit, if 0, is changed to 1. The translating circuit TC operates as follows. When bi-stable circuit T4 is triggered gate G18 is opened and stimulates control wire 11 of gates G24 to G27, thereby taking the complement of the output from the reading heads. By virtue of gate G22, 1 is subtracted from the digits stored in spaces t5 to t7. If during this channel time when the binary numbers are being changed and written in one storage compartment and read in their first binary form in the other storage compartment, it happens that the eights digit in space t8 is 1, which is true for first impulse trains of. 1 to 7 impulses, or the digits in spaces t5 and t6 are each 1, which is true for 8 impulses in the first impulse train, then bi-stable circuit T7 or bi-stable circuits T5 and T6 remain unoperated and permit gate G23 to write 1 in space t8 and gate G47 to write 0 for the eights digit in space t12. When the first train has 9 impulses it is uniquely determined that 0 will be read at t5 and t8 and 1 will be read at t6, thus bi-stable circuits T5 and T7 are operated to open G19 and write 1 for the eights digit in space t12. When the first impulse train has 10 impulses it is uniquely determined that 1 is read at t5 and 0 is read at t6 and t8; thus bi-stable circuits T6 and T7 are triggered to open G20 and write 0 in space t8 while G47 is opened to write 0 for the eights digits in space t12. The binary number now stored in the spaces t5 to t8 is suited to control the untimed metering circuit UMC whereby a number of pulses is applied to the subscriber's meter at the beginning of a call regardless of duration, while the number stored in spaces t9 to t12 is suited to control the rate at which pulses are applied to the subscriber's meter by the timed metering circuit TMC. The writing in spaces t13 to t16 remains 1111. Metering regardless of duration.-With a first impulse train of 1 to 8 impulses and a second impulse train of 8 impulses the spaces t5 to t8 register a binary number which requires as many subtractions of 1 to change the digit in storage space t8 to 0 as there were impulses in the first train, while the spaces t9 to t12 register 0000. In the absence of 1 read in the spaces t9 to t12, gates G35 to G38 in the timed metering circuit remain closed and in consequence sources of pulses P1, P2, P4 and P8 are disconnected. In the untimed metering circuit a source of pulses Po, recurring at 2 per second and of a length equal to half a revolution of the magnetic drum, is connected to a gate G28. When the called subscriber replies, relay D responds and stimulates the backward hold multiplex MX2 which puts pulses on the highway 37 during the relevant channel time. Gate G28 is thereby opened during consecutive pulses of Po and energizes the control lead 25 of subtracting circuit SC to reduce the binary number registered in spaces t5 to t8 by 1. So long as gate G29 is kept open at time t8 by a 1 read in space t8 the input highway of metering multiplex MX1 is stimulated and, over a pulse lengthener L2, operates relay J to connect battery to the subscriber's meter by way