Abstract: In a first preferred embodiment of the invention, a clip-on switching device is disclosed to prevent the placing of unauthorized outgoing calls from a (Touch Tone) telephone and/or to selectively switch an incoming call to an accessory (extension) telephone circuit. The switching device includes a housing which is particularly shaped to conform to the contour of the telephone cradle so as to be releasably connected therewithin. Positioned within the housing is a card having a control circuit thereon for selectively controlling the telephone circuitry. A unique spring-biased light emitting diode push-button switch is associated with the instant switching device, whereby to provide a visible signal, so as to indicate the operation of the telephone control circuit.