GB1252620A - - Google Patents

Abstract

1,252,620. Telegraph exchanges. SIEMENS A.G. 10 Dec., 1969 [11 Dec., 1968], No. 60238/69. Heading H4P. In a telegraph exchange system having a plurality of single-current/double-current converter circuits, wherein during the development of a connection, a controlling exchange transmits a monitoring signal to a particular selected converter circuit, each converter circuit is designed to allow the received monitoring signal to be reflected to the controlling exchange, which is adapted to analyse the transit time and/or the duration of said reflected monitoring signal in order to ascertain the operational condition of the converter circuit affecting that particular reflection. In Fig. 2, which is similar to Fig. 1 (not shown), contact (f) is omitted hence a signal on wire b2 is reflected on wire a2 the polarity of which depends on the condition of the converter circuit. If a controlling exchange supplies a monitoring pulse to b2, contact b contacts with +TB polarity hence winding A1 is energized. Contact a is also connected to + TB polarity hence this is reflected back to the controlling exchange. Each converter circuit may be permanently assigned to a subscribers line, for example, in the case of a TDM exchange (see Fig. 4, not shown). In this arrangement line a1 is connected to line b1 through contacts (sk) which are closed in a dialling condition thus energizing receiver relay (EM).