Patent GB-787543-A (GB)
Title: Improvements in or relating to circuit arrangements for use in telecommunication installations
IPC: H04Q3/00
Filed: 1956-01-20
Abstract: 787,543. Automatic exchange systems. SIEMENS & HALSKE AKT.-GES. Jan. 20, 1956 [Jan. 22, 1955], No. 2041/56. Class 40 (4). A selector is capable of switching an incoming two-wire line to a further two-wire line or, in response to a predetermined signal, of switching the incoming two-wire line to a four-wire line by connecting the two-wire line to the two-wire side of a two to four-wire terminating unit and by connecting wipers of the selector to the four-wire side of the unit. The predetermined signal may be the initial digits 0 or 00 of a dialling code. In Fig. 4 an incoming two-wire line VL is shown connected to wipers of a rotary selector IGW which has two pairs of two sets of four wipers, each pair moving in synchronism over respective banks of 50 contacts each. The first pair of wipers comprises the sets au, bu, cu, du, and alu, blu, c1u, d1u, which are set in response to any dialled digit 1 to 5, each digit carrying the wipers over a group of ten contacts. When set on any of the five groups the wipers hunt across the ten contacts of the group in search of an idle line. In response to any digit 6 to 0 the first pair of wipers pass through their contact banks without being set and on the 6th digit the second pair of wipers ao, bo, co, do, and alo, b1o, c1o, d1o, engage their contact banks which are also divided into five groups of ten contacts each. In the last group, reached by the digit 0, the first five contacts of the group are wired to two-wire circuits and the second five to fourwire circuits. The test wipers co, c1o, hunt simultaneously over pairs of ten possible twowire outlets and should both test relays P1, P2 respond together one disables the other in a manner not shown. The responding test relay halts the selector by energizing both field windings of the driving magnets M1, M2, and connects the incoming and outgoing lines over the appropriate wipers. The outgoing two-wire lines terminate in a group selector and, if the next digit of the dialling code is also 0, this selector operates a tenth level contact Dko to connect earth over wiper do or d1o of IGW to pull back relay U over its first winding. U locks up over its second winding in dependence on a contact of a relay C which holds up as long as the call lasts. Relay U in locking up pulls back slow-to-release relay UH and connects the hitherto alternative sets of wipers into the four output wires of a two to four-wire junction G, with a balancing network N, and connects the two-wire line VL to the input of G. Contacts of relay U disconnect test relays P1 and P2 from the two-wire test circuits and connect relay P2 as a test relay for the five four-wire circuits over wiper d1o. Disconnection of the energized test relay releases the field windings of magnets M1, M2, and advances the selector over the last five contacts of the group in search of an idle fourwire line. If the incoming line VL is released relay C falls back and releases relays U and UH, the selector homing in a normal manner. In the event of connecting to a four-wire circuit in response to the digit 0 alone, selector IGW is arranged to operate a tenth level contact dkx which pulls back relay U and UH and effects the two to four-wire connection without the necessity of finding an idle two-wire outlet first. The arrangement responding to the digits 00 is shown embodied in an exchange in Fig. 2 where the line VL terminates in a repeater UK and where IGW has access to two-wire local lines Li over the first four groups and to two-wire lines La to an outgoing repeater Ug over the next five groups. The tenth group is split between two and four-wire lines going to a service group selector DGW and a selector MW respectively. The four-wire lines are connectible over an operator's incoming position VL and trunk record position MPL and selectors IFGW, IIFGW, to outgoing four-wire lines FL; and alternatively over IFGW and via a two to fourwire terminal unit G to the repeater Ug and its associated outgoing two-wire lines. The arrangement responding to digit 0 alone is shown in Fig. 3, where the whole of the tenth group of IGW is set aside for four-wire lines having access over a group selector DGW to service two-wire lines or the outgoing two-wire and four-wire lines associated with repeater Ug and selector IIFGW respectively. The groups of contacts in the selector IGW may be varied and if groups of five are used one bank of fifty contacts can provide ten groups using eight wipers in place of sixteen required with groups of ten. Alternatively, sixteen wipers may be used with the groups of five contacts so that hunting takes place over four sets of five two-wire outlets simultaneously or two sets of five fourwire outlets in which event four test relays are required.