GB1341429A - Mobile radio telephone system - Google Patents

Abstract

1341429 Automatic exchange equipment SOC ITALIANA TELECOMUNICAZIONI SIEMENS SpA 19 April 1971 [9 Feb 1970] 22233/71 Heading H4T The fixed installation of a radio telephone system includes a programmer and a code converter which supervise the system and translate the signals emanating from the mobile user or the exchange into a form suitable for the other. Timing circuits are provided to ensure that if each stage in the connection process is not completed a clearing signal is generated to release the connection. In operation each free radio channel radiates an availability tone which is sought by a particular mobile user when it receives a call signal from a general calling channel. When the mobile locks on to this channel it sends a carrier frequency signal PR which operates switching circuit αS to stop the radiation of the availability signal and start monostable M2 which provides the second timing circuit. Within the time period of M2, 300MS, the mobile should radiate its identification signal IM which sets bi-stable B3 and by-passes M2. Depending on the direction of the call either a calling signal ch or dial tone sc is sent to the mobile and monostable M1 which forms the first timing circuit, having a period of 45 secs., is set. When the mobile's handset is lifted, signal r disappears to set bi-stable B2 through gate 13 and thus by-pass M1. Similarly if the mobile's dial is operated bi-stable B2 is set and M1 by-passed. The monostable M3 is used to cause the sending of a clearing signal which restores the equipment to its original condition. Monostable M3 is set by the output of gate 18 which has inputs from the timing circuit monostables M1, M2, from the exchange ds, from the mobile signal r and also from circuit α 5 which responds, after a 5 sec. delay, to loss of carrier signal and error signal E which is sent from the code converter when an error in code is perceived.