A telephone security device is built into a telephone unit. The device includes a sensor to detect an intrusion into the area in which the telephone is located. Upon detection of an event, the device places the telephone off hook, and triggers the redial feature of the telephone. This causes the telephone to redial the last number that had been called. The telephone then remains in the off hook condition for a delay interval to allow the recipient of the call to listen, via the telephone, for any sounds indication that an actual intrusion has occurred. In order to arm the security device, the user simply dials the number that is the intended recipient of the call, hang up, and switch on the sensor. Detection of a security event will then cause the last dialed number to be redialed.