Patent GB-654883-A (GB)
Title: Improvements in or relating to telecommunication exchange systems
IPC: H04Q3/42
Filed: 1948-04-26
Abstract: 654,883. Automatic exchange systems. STANDARD TELEPHONES & CABLES, Ltd. (Bell Telephone Manufacturing Co. Soc. Anon.). April 26, 1948, No. 11427. [Class 40 (iv)] In a long-distance telecommunication exchange system an operator at one exchange may dial a special digit not normally used for setting up subscriber calls, whereby access to a service P.A.B.X. can be obtained over which she may transmit selective signals to obtain a predetermined one of a group of operators' positions at another exchange. In addition a particular connecting circuit at that operator's position may be selected. The invention is described with reference to the international system described in Specification 645,303 in which an operator in one country can set up calls in another country if necessary via tandem exchanges in other countries. A first operator after an unsuccessful attempt to set up a call in a second country transmits via her key-set register IKR, the international code of the wanted country followed by the " digit " 11 (a four-element binary transmission code is used giving 10 signals for ordinary digits and 6 others for special purposes such as the one now being described). At the second exchange a national link and a national register NR are seized, the latter responding to the "digit" 11, to cause the national link to be seized by a finder associated with an operator's position wherein a special lamp lights to indicate that the call is from another operator. The second operator notes the particulars of the wanted subscriber and also the first operator's position number and when she has established contact with the former she transmits via the key-set register IKR the international code of the originating country; the " digit 12; the number of the wanted operator's position; and the digit 0 (indicating that any free connecting circuit on that position will do). At the first exchange a national link and national register NR are thereby seized, the latter responding to the " digit " 12 to cause the national link to be connected to a service P.B.X. link which is then set by the position number and the digit 0 to a free connecting circuit on the first operator's position. The second operator then tells the first her position number and the number of the connecting circuit to which the wanted subscriber is connected. The first operator then transmits these numbers preceded by the international code of the second country and the " digit " 12, whereupon the connection is established via the national link and the service P.B.X. to the required connecting circuit. The second operator is thereupon cutout of the connection, but a busy lamp associated with the connecting circuit is lit at her position. Calling procedure. The second operator's calling lamp is not lit at the end of selection, indication of this being given only to the first operator who may then in her own time send a forward signal to call the second operator. Besides facilitating the operators' duties this arrangement avoids the need of a special non- meter answer-back signal for calls to operators' positions. In order to avoid language difficulties the national registers are equipped to recognise calls for subscribers on manual exchanges and to direct them to an operator. All setting up signals may be accompanied by the identity of the calling country which is then used to direct calls to an operator speaking the appropriate language. Specification 642,541 also is referred to.