Abstract: A telephone privacy and alerting device for connection between a common telephone line and a telephone device. The privacy and alerting device includes a privacy circuit to prevent the telephone device from accessing the telephone line when another telephone device is already off-hook, and an alerting circuit to indicate an alarm when the telephone device is off-hook and a further telephone device is also off-hook. The privacy circuit includes a voice connecting circuit for connection between the telephone line and the telephone device, a self-latching switch means connected to the voice connecting circuit having an on and off state, and voltage breakdown means for turning the self-latching switch means on when a closed circuit is provided through the telephone device and the potential across said telephone line is above a first predetermined threshold, thereby allowing the voice connecting circuit to establish a current path between the telephone line and the telephone device.

Abstract: A telephone alerting device for connection to a telephone line and a telephone. When the telephone is off-hook, the device will generate a visual and an audio alarm if an additional telephone connected to the same line also goes off-hook, thereby providing an eavesdropping alarm. The audio alarm is a periodic signal of short duration heard in the ear-pieces of all off-hook telephones connected to the telephone line. The device includes a voice path having a resistor placed in series with the telephone for raising the voltage across the telephone line when the telephone alone is off-hook. In order to trigger the alarm, the telephone must be off-hook and the voltage across the telephone line must be below a threshold value.

Abstract: A telephone privacy protector for connection to a common exchange line and each one of at least two telephone operated devices sharing a line includes a voice connecting circuit for connection between a respective telephone line operated device and the line. There is a control deice connected to the circuit having an on and off state wherein the control device in the on state permits the voice connecting circuit to operate. There are means for turing the control device on when the respective telephone line operated device goes off hook provided that no other telephone line operated device sharing the line is off hook. There are means for providing a residual charge to the control device in order to reactivate same after the respective telephone line operated device is placed momentarily on hook and then returned to an off hook state while any other telephone line operated device connected to the line is off hook.