| 摘要 |
Telephone command apparatus responsive to ringing current on a telephone line includes a decoder responsive to upper and lower frequency components of two-tone signals and an access and lockout device responsive to decoded signals representative of a correct sequence of two-tone signals for terminating the incoming telephone line and enabling a plurality of relays for actuation selectively in response to other two-tone signals received over the telephone line to initiate and complete one or more operations at the called location. Until the correct sequence of two-tone signals is received, the command apparatus has no effect on the telephone line to which it is connected and the line functions in the normal way. Transmittal of an incorrect series of two-tone signals to the access and lockout device disables the command apparatus and renders it incapable of responding to incoming signals for a predetermined period of time. Selected interrogating two-tone signals transmitted by the caller condition an oscillator to generate audible signals of different frequency to indicate the "on" or "off" status of a selected operation. Relay means responsive either to a selected two-tone signal or to a dial tone or other permanent signal on the line disconnects the command apparatus from the line and readies it for the next incoming call.
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