wireless personenrufanlage with sprachdurchsage

摘要

The paging system uses the same modulated carrier frequency for calling a selected portable receiver, characterised by a particular call telegram, and for relaying the message to a second portable receiver. Preferably the central transmitter has a speech frequency voltage source (11), connected via a high-pass filter (12) with the modulation input (2) of a high frequency source (1), and a data source (8), connected via a low-pass filter (10) with the modulation input (2) of the high frequency source (1). Each portable receiver has a demodulator connected to a decoder via a low-pass filter, and to a loudspeaker circuit via a high-pass filter. The loudspeaker circuit can be switched between an audio frequency source and the output of the high-pass filter.