Patent GB-944162-A (GB)
Title: Improvements in or relating to automatic telephone exchanges
Inventor: BRAY FREDERICK HARRY
IPC: H04Q3/00
Filed: 1959-07-09
Abstract: 944,162. Automatic exchange systems. STANDARD TELEPHONES & CABLES Ltd. July 8, 1960 [July 9, 1959], No. 23608/59. Heading H4K. In an exchange of the type described in Specification 794,812, register switching equipment RSN, additional to and separate from the main switching equipment MSN carrying speech or supervisory signals, is provided over which equipment RSN a connection is set up from a register REG to the circuit associated with an outgoing junction, over which connection the signals necessary for completing a call to a distant exchange are transmitted. Local calls are set up as described in Specification 794,812 with the exception that subscriber's lines are not scanned to detect calling lines. The switches employ the double anode-single cathode tubes of Specification 734,345 as cross-points. Class-of-service detectors CSA, CSB are provided, one per class, each of which is connected to all the lines of its class, and to all the registers, such as REG. A class-of-service distributer DCS scans the registers and, on finding a newly seized one, stops and causes the register to transmit a super-audio (8 kc/s.) identification signal which passes via the register hunter RH, first link 1L, terminal connector TCA and the calling line circuit LC to the detector, say CSA. CSA sends the relevant class-of-service signal which is effective only on the register which sent the identification signal, wherein the information is stored. DCS is released and continues its scanning. The register reverts dial tone and the caller dials in the usual way. When the register has sufficient information to commence setting-up the call, the call distributer DNC gives it a " go head " signal, whereupon it transmits the wanted line number to the called line marker CLM, and transmits the class of service and the meter rate over leads C and M respectively. Outgoing calls.-If the exchange digits received by the register denote such a call, the register assumes its condition of readiness immediately, and (when DNC permits it) sends the exchange digits to the marker CLM, which marks via leads MH and TU a group of junctions giving access to the wanted exchange. These may be direct junctions. DJ, tandem junctions TJ, or subscriber trunk dialling junctions STD, over all of which digits are sent as D.C. impulses. For each junction group there is an AND-gate such as G2, G3, G4 and a junction scan circuit such as JSS, JST, JSD. Assuming that the call requires a tandem junction of the group to which TJ belongs, CLM opens G3 and JST tests for a free junction, and on finding one, marks the corresponding junction circuit TJL which acts as a final link therefor. The timed control of the exchange now causses the link TJL and the register REG to mark the appropriate outlet and inlet of the additional switching network RSN which is a primary/secondary/ tertiary array similar to, but smaller than, MSN. A route selector RSB then selects a free path through RSN over which the register is connected to the link TJL. During this time the register has been receiving the numerical digits and now starts to send as much as is needed of the dialled digits via the network RSN and link TJL to the seized junction TJ. In the case of a tandem junction this includes either the exchange code or. a translation thereof, and the numericals, this information being sent to the link TJL as V.F. pulses, and being there converted into D.C. impulses for transmission over the junction. After the last digit has been sent, the register signals the link TJL which then marks itself as an outlet from MSN. The register REG releases whereupon the first link 1L marks itself as an inlet to MSN and the route selector RSA sets up the required speech path via MSN. The release of REG breaks down the connection via RSN. Calling subscriber release is provided. Metering.-The register sends the meter rate to TJL before the first link is connected to the junction and TJL sends meter signals at the appropriate rate to operate the meter detector MD associated with the calling line. Specification 944,163 also is referred to.