| 摘要 |
A device for selectively ringing a specific party in a multiparty telephone system by frequency discrimination including a remotely actuable solid state switch connected in series with the telephone circuit of each customer. A programmable frequency discriminator is connected across the customer's telephone circuit for opening the solid state switch in response to a ringing voltage. A frequency discriminator produces an output signal in response to the ringing voltage of a selected frequency preprogrammed into the discriminator. The output of the frequency discriminator is connected to an AC to DC to AC converting circuit which is connected within the customer's telephone circuit. The frequency discriminator enables the converting circuit which thereby converts the frequency of the ringing voltage to a standard 20 Hz for ringing the customer's phone.
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