Patent GB-1149187-A (GB)
Title: Improvements in or relating to automatic telephone systems
Inventor: MURRAY LAURENCE JOHN
IPC: H04Q3/00
Filed: 1966-07-14
Abstract: 1,149,187. Automatic exchange systems. AUTOMATIC TELEPHONE & ELECTRIC CO. Ltd. 29 June, 1967 [14 July, 1966], No. 31649/66. Heading H4K. In an exchange having a group selector which comprises at each stage a plurality of link-connected primary and secondary reed relay matrices which are controlled by individual register/markers, local and direct outgoing junction calls are set up over first and second group selectors with the aid of an originating register (in which all dialled digits are recorded) and the register/markers pertaining to these two stages of the group selector whereas calls which cannot be routed directly viz. tandem calls, are set up over first and second or first, second and third group selectors with the aid of a translator taken into use at the second selector stage. The reed relay switching stages and their manner of control are described in Specification No. 1,131,367. In the present disclosure a primary and secondary crosspoint group in each stage is represented by a box containing crossed diagonals viz. 1S 2S, 3S, the outlet levels of a group being shown below its box as a vertical set of horizontal lines numbered 1-0 upwardly. There is no direct relationship between the number of a level and the exchange codes viz. ABC digits which are associated with it, i.e. calls in which the AB digits are 11, 21, 59, 62, 65, 77, 81, 95 will all be directed to a free outlet in level 8 of selector 1S under the control of the first group selector's register/marker, to which the AB digits have been forwarded in multipotential code form by an originating register OR. Operation, all calls.-A calling subscriber is initially connected to a register access circuit ORAC which has an individual appearance on first group selector 1S. The access circuit is connected via a register connector ORC to an originating register OR which is normally used for recording all the digits dialled by the subscriber. STD call.-The register recognizes the first digit, i.e. 0 as being in respect of an STD call and immediately causes the first selector's control circuit to seize a free outlet in level 0. The subscriber's loop is extended over this level so that the later digits are repeated direct to the STD equipment. The originating register drops out immediately the loop is extended. Local or direct junction call.-The register awaits reception of the first two or three digits and then seizes IS's control circuit. The latter reverts a proceed-to-send signal and then accepts the AB digits. For the call considered, an outlet in the appropriate one of levels 2-8 is selected and the first stage crosspoints for connecting ORAC to this outlet are closed. 2S's control circuit is seized whereafter IS's control circuit is released. In response to a proceed-to-send signal, the register transmits the BC digits in coded form to 2S's control circuit. The latter seizes and connects through to an appropriate outlet, local or direct outgoing junction as the case may be, and then reverts a special signal to the register. In response thereto, the latter transmits the numerical digits in coded or 10 i.p.s. form to the local reed relay connector or to the junction. If necessary a third group selector operating in a similar manner may be seized. Tandem call.-Such a call may be routed to a translator access circuit TAC (2) from the 1 level of the first selector or to a similar circuit TAC (3) from the 1 level of the second selector. In either case, a translator 3DT is reached via the appropriate translator connector TCA or TCB and in response to a proceedto-send signal the originating register transmits to 3DT the A, B and C digits. The first routing digit supplied by 3DT in coded form is used to set the second or third group selector as the case may be and the remaining digits (up to five) are sent in 10 i.p.s. form direct to the tandem junction when the distant exchange reverts a proceed-to-send signal. When this transmission is complete the translator, the translator connector and the second or third group selector control circuit are released whereafter the originating register transmits the remaining digits direct to the junction in 10 i.p.s. form. Tandem call, alternatives.-If only one tandem junction is provided, it may be accessed directly via translator access circuits connected to the 1 levels of the first and second selectors (Fig. 2, not shown). As a further alternative, all of the levels from the first selector (except the 0, STD level) are connectible to second selectors, the 1 level not being reserved for tandem traffic (Fig. 3, not shown).