A long distance automatic teleprinter exchange with manual priority service

The system described is designed to interconnect stations in the Southern area of the L.N.E.R. A point to point teleprinter system has been in operation in the Northern area for some time. The problem in front of the designers was high traffic and limited line plant available. The traffic is made up of urgent and non-urgent messages. The urgent messages have precedence over all other forms of traffic. All trunk offering is carried out by a central supervisor who can enter in on any existing connexion. Thus local connexions are obtained automatically and the attendant handles what is equivalent to exchange traffic. The line plant consists of open wire earth return circuits some of which were superposed on telephone channels. Supervisory indications from the exchange such as "busy," "unobtainable" are generated by a special sender and automatically printed at the calling teleprinter. The paper includes photographs of the equipment.