Some recent developments in teleprinter switching systems
14 January 1938
In the teleprinter switching systems described the terminating equipment of all lines is provided with repeaters or converters, each comprising a sending and receiving telegraph relay. This converts all types of line into an equivalent system thus permitting them to be readily interconnected with each other and with any type of telegraph channel (single or double current or voice frequency). The substation equipment includes the provision of a control box which carries a calling dial, a starting key, a release key, a control lamp, and the necessary apparatus for controlling the teleprinter motor. The paper describes the arrangements of an automatic exchange for 100 lines and those for one of 10 lines capacity. The equipment is illustrated by photographs, and trunking diagrams are given of typical connexions. The operations in setting up a connexion between two subscribers are explained and broadcast connexions dealt with. The narrow frequency band width required for telegraph transmission as compared with telephone transmission permits a considerably more economical use of line plant.