| 摘要 |
1. An electrical circuit of a voice signalling system, for use in an automatic telephone network, equipped with signal amplifiers connected to primary windings of a balancing transformer, whose secondary windings, connected through transmission attachments to the units of a telephone exchange, are loaded with resistance ensuring appropriate crosstalk attenuation between subscribers connected in parallel, whereas the remaining transformer secondary windings are connected to sound control modules, whose terminals are situated in the alarm circuit of the system, characterised in that at the input it has a sampling frequency generator (1), whose output is connected to the address input of the address counter (3), and the input of that generator (1) is connected, through a monovibrator (2), to the timing output of the counter (3), whereas the address outputs of the counter (3) are connected, through the address bus (MA), to the inputs of two EPROM memories (4), whereas the outputs of the memories (4) are connected by 8-bit data buses (MD) to inputs of digital-analogue transducers (5), loaded with band amplifiers (6)connected to the primary windings of the balancing transformer (Tr), whose secondary windings are connected to units of the exchange, all functional elements being supplied with power from a balanced voltage converter, at whose input is a self-excited wave generator (8)...<IMAGE>
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