Patent GB-570415-A (GB)
Title: Radio signalling system calling arrangements
IPC: H04W84/02
Filed: 1943-12-04
Abstract: 570,415. Automatic exchange systems. MURDOCH & CO., Ltd., J. G., CLAY, D. L., and HOGG, F. L. Dec. 4, 1943, No. 20307. Drawings to Specification. [Class 40 (iv)] [Also in Group XL] In an intercommunicating radio-tolephone system comprising a number of stations each having a receiver set to its own predetermined frequency and a transmitter which can be set to the receiving frequency of any other station, the dialling pulses at a calling station serve to set the transmitters at the called and calling stations to each other's receiving frequencies, puts the called transmitter into operation and calls the station. The system according to the invention is applicable to direct automatic radio-telephone communication between members of the group of stations each having a wireless receiver and transmitter, or between members of different groups through the medium of powerful master stations each common to a group of stations. It also allows automatic connection of a radio station to a wired telephone system through a master station, although the reverse connection from the wired subscriber to a radio subscriber requires the intervention of an operator at the master station. Each station has its own receiving wavelength, and its transmitter is adjustable to the respondent's receiving wavelength. The dialling system for calling includes three stages. The first number dialled is special to the respondent and performs three main functions (a) tunes caller's transmitter to respondent's receiving wavelength, (b) tunes caller's receiver temporarily to the same wavelength, (c) tests if this wavelength is busy and sets the local apparatus accordingly. The second number dialled is a standard one common to all stations and is radiated on respondent's receiving wavelength if this is free. It serves (a) to start heating the valves of respondent's transmitter and (b) to prepare circuits for tuning respondent's transmitter. The third number is the calling station's own number and serves (a) to tune respondent's transmitter to the calling station's receiving wavelength, (b) to complete the call by operating respondent's bell or buzzer. The control operations are effected by means of plain carrier wave and carrier wave modulated by a 1000 cycle tone. For connection between a radio subscriber and a wired subscriber, a master station is required. In this case the first number dialled is the master station's number as before, the second number is again the master station's number and serves to connect the receiver output of the master station to the wire line. The third number is the standard number for energizing the master station at the end of which process the caller gets a special wired dialling tone. The fourth number or numbers are the wired subscriber's number and calls the wired subscriber in the usual way. In this case the call must be cleared by the caller. A wired subscriber calls a radio subscriber by giving the number to an operator at the master station who makes the connection. This facility is also available to a radio subscriber who fails to get the number by dialling.