| 摘要 |
Apparatus for enabling or disabling a selected telephone. A control signal having a unique predetermined frequency, which corresponds to a desired state of the selected telephone, is transmitted from a transmitter through standard telephone lines. The telephone is connected to a receiver, having one of a plurality of resonant circuits each tuned to one of the unique predetermined frequencies, which receives the control signal. When the frequency of the control signal matches the tuned frequency of a resonant circuit, the receiver connects or disconnects accordingly the selected telephone from the telephone lines thereby enabling or disabling, respectively, the selected telephone.
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