Patent GB-817421-A (GB)
Title: Improvements relating to automatic exchange systems
Inventor: FLOOD JOHN EDWARD
IPC: H04M15/04
Filed: 1954-10-02
Abstract: 817,421. Automatic exchange systems. SIEMENS EDISON SWAN Ltd. Dec. 23, 1955 [Oct. 2, 1954], No. 19486/54. Class 40 (4). A system with a common marker or a common translator has multi-metering arrangements including a device with a number of storage compartments, at least one compartment for each path through the exchange, and includes means whereby metering information from the marker or translator in respect of a call is stored in a compartment selected, according to the path appropriated for the call, as the result of the receipt of one or more signals indicative of the said particular path. The storage compartments are associated with the respective paths by means of a time-division multiplex system. General arrangement, Fig. 1. Electronic switches are shown schematically as wiper switches. When a trunk 100 assumes a calling condition a connection to a register translator RT is set up automatically by way of an incoming switch IS and a register switch RS. The dialled digits are registered in RT which transfers translated information to a common marker CM as soon as the latter is free. The common marker CM marks the called trunk or group of trunks 101 and passes metering information to common multi-metering equipment MM. The marking applied to 101 is extended backwards over all idle paths to the relevant incoming switch IS. A connection is set up over one of these paths by a forward hold signal from the first selecting switch SS. The common marker is then released to remove all backward markings. The register-translator RT is released when it receives ringing tone. For a local subscriber ringing current is applied from the supervisory link circuit SLC. When the call is answered a backward hold signal trips the ringing for a call to local subscriber and establishes the conversational path. For a call from a local subscriber the common multimetering equipment MM responds to the backward hold signal to apply metering pulses to the supervisory link circuit SLC. Metering. General arrangement, Fig. 2. Wires 104-107 form part of a supervisory link circuit SLC. Each circuit SLC has a pair of storage compartments on the track MSD of a magnetic drum, one compartment passing the reading head RH as the other passes the write head WH. Each compartment has 8 element storage spaces divided to store two numbers each of four binary digits, the corresponding time periods being t 1a -t 4 a and t 1 bt 4b . The link circuits SLC are associated with the drum over four time-division multiplex circuits TDM1-TDM4. As long as a link circuit is normal the writing in the associate element storage spaces is O. When a link circuit SLC is appropriated for a call a backward marking condition from the common marker appears on wire 104 and a forward hold condition from the relevant first selecting switch on wire 105, and the common marker pulses one or more of the 8 signal wires 103. The markings on 104 and 105 cause multiplex circuits TDM1 and TDM2 to apply pulses pertaining to the link circuit to writing control circuit WCC to enter 1 in element storage space t 1a -t 4b  according to whether a pulse has been applied to the first eighth signal wire 103. For untimed calls 1 is entered in t 4a  and the metering number, reduced by 1, is entered on the binary basis in t 1a -t 2a . For timed calls the metering number per minute is entered on the binary basis in t 1b -t 4b . When the call is answered a mark on backward hold wire 106 causes pulses pertaining to the link circuit to appear in the output of multiplex TDM4. This causes a pulse to be applied to metering multiplex TDM3 during one or more channel time periods pertaining to the link circuit, so pulsing the metering wire 107 extending to the calling subscriber's meter a number of time depending on the entry in storage spaces t 1a - t 4b  and, if the call is metered on a timed basis, on the duration of the call. For metering on an untimed basis pulses P 0 , Fig. 3, are supplied lasting for half the time of revolution of the drum. Each time the backward hold multiplex TDM4 issues a pulse in respect of the link circuit SLC it combines with a P 0  pulse to reduce the number in the related storage space t 1a -t 4a  by 1 while a pulse is fed by multiplex TDM3 to the metering wire 107  of the calling subscriber's line. The last pulse changes t 4a  to 0 and the remaining spaces to 1, further pulses to wire 107 being then inhibited. For metering on a timed basis pulses P 1 , P 2 , P 4'  P 8  with recurrence frequencies of 1, 2, 4, 8 per minute, respectively, are supplied. Each of these pulses lasts for one revolution of the drum and are spaced in time from one another. Each time 1 is read in one of the spaces t 1b -t 4b  at the same time as one of the pulses P 1- P 8  exists a pulse is applied to the metering multiplex TDM3 during the channel time concerned. Detailed description, Figs. 4A and 4B. For each pair of storage compartments there is a primary channel-selecting train of pulses such as W, each pulse covering four consecutive pairs of storage compartments. The individual pair of storage compartments is further defined by one of four secondary channel-selecting pulse trains S 1 -S 4.  In the drawings the storage compartments are those pertaining to pulses W and S 1 . While the link circuit SLC is idle gating circuit G18 pulses wire 11 to write 0 in all the associated storage spaces. Untimed calls. When the link circuit is taken into use, assuming the call is metered on an untimed basis, there appear a backward marking condition on wire 104, a forward hold condition on wire 105, a mark on wire FL4 and a mark on one or more of wires FL1-FL3 and a mark on one or more of wires FL1-FL3 equivalent to the charge for the call reduced by 1 unit. In the appropriate time period, therefore, gates G11 and G16 pulse wires 13 and 22, respectively in all eight element time periods. Gates G1-G8 receive pulses t 1 -t 4  as shown and gates G9, G10 receive pulses t a , t b . According to the leads FL1-FL4 which are marked so, in the example, G9 passes appropriate pulses t 1a -t 4a  to wire 26. G12 passes these pulses to wire 19 and also inhibits G15. The pulses on wires 19 and 13 combine at G17 to enter 1 in the spaces t 1a -t 4a  corresponding to the marked wires FL1-FL4. Trigger circuit T1 normally marks wire 42. When the reading head RH encounters 1 in an element storage space during the relevant reading control pulse K R  it operates trigger circuit T3 to mark wire 34 so that G29 pulses wire 35. This pulse passes G28 opened by the mark on wire 42 to rewrite 1 in the space. When 0 is read trigger T2 operates to pass a t a  pulse through G24. This pulse combines with the mark on wire 42 to pass through G25 so that 0 is rewritten. T2 and T3 are reset at the beginning of the next element by driving control pulse K D . When the call is answered and a backward hold mark appears on wire 106 gate G35 pulses wire 51 at each channel time period pertaining to the link circuit. At each such time when a pulse P o  exists the pulse on wire 51 passes G34 and G32 to operate T1 which then marks wire 40. Readings in successive elements are reversed until a 1 is changed to 0 when TI is restored. Thus when the reading head encounters 1 T3 operates as before but this time the mark on wire 40 causes G27 to pulse wire 10 to write 0 in the space. On the other hand, when 0 is read a pulse appears on wire 47 which combines with the mark on wire 40 to cause G26 to write 1. When 1 is changed to 0, signifying the completion of subtraction by 1, a control pulse Kp combines with the pulse on wire 35 to cause G31 to reset T1, the remaining elements of the storage space being then rewritten unchanged. When 1 is read in t 4a'  however, gate G33 pulses wire 54 to cause the metering multiplex to pulse the wire 107 extending to the calling subscriber's meter. The corresponding elements on the other half of the drum are likewise changed. The process repeats until the 1 in element t 4 a has been changed to 0, after which no further pulses are delivered to wire 107 because gate G29 is no longer operative. Timed calls. Metering takes place on the basis that an initial charge of 1 is made, followered by charges at say 12 meter operations per minute. The initial operation of the meter takes place as in an untimed call, the number in elements t 1a -t 4a  being changed from 1000 to 0111 and a pulse being sent to the meter. Each time the O in t 4a  is then read a pulse appears on wire 66 so that G41 operates trigger T4 to mark wire 62. T4 is reset by G42 at the beginning of the next channel time period. According to whether the metering marks are in elements t 1b ,  t2b , t 3b , t 4b , so when a pulse P 1 , P 2 , P 4 , P 8  exists gates G36, G37, G38, G39 pass a pulse from the reading head so that G40 pulses wire 63 to enter 1 in the meter. The pulses P 1 , P 2 , P 4 , P 8  have a frequency of 1, 2, 4 and 8 per minute so that the requisite number of metering pulses is made for each minute of the duration of the call.