GB1482525A - Telephone systems - Google Patents

Abstract

1482525 Automatic exchange systems GENERAL ELECTRIC CO Ltd 6 Nov 1974 [6 Nov 1973] 51376/73 Heading H4K A telephone substation includes a two dimensional array of push-buttons, connected to a central switching apparatus by conductors individually associated with the rows and columns, selection being effected by operating a button to interconnect a row conductor and a column conductor. In the enquiry system described ten or twenty enquiry desk substations are each provided with a 10 Î 10 array of keys 6 controlling directly in co-ordinate fashion corresponding relays of a subscriber individual matrix giving access to corresponding subscriber lines. The row and column driving transistor circuits 10 and 11 are supplied via corresponding transistors 18, 19 controlled by Schmitt triggers 16, 17 which prevent double connections by releasing any existing connection during a new connection. The enquiry desk substations can connect to and cause ring- ing to be applied to any selected subscriber line. A call from a subscriber to the enquiry centre causes a lamp to flash in association with the corresponding key at each enquiry desk substation any of which can respond by depressing that key, the flashing signal being changed to a steady signal at that time. The power, tone and lamp supply arrangements are described. The enquiry desk subscribers may also be connected on a PAX line for communication within a group and the manner in which a hold relay may be used to hold a connection on the PAX line while clearing and effecting a connection over the central switching apparatus is outlined.