| 摘要 |
A protective alarm for automatically connecting itself to a telephone line, dialing a remote telephone and delivering an audio message to the remote telephone, in response to an intrusion. The alarm has a magnetic tape and an associated tape player. On the tape is recorded a 5-kilohertz control signal 100 percent modulated by telephone dialing pulses which are followed by an oral message that is superimposed on the continous control signal. A dialing switch connects the audio output of the tape player to the telephone line when an intrusion switch located, for an example in a window, is opened. A bi-polar transistor controls the dialing switch. The transistor is biased to cause the dialing switch to disconnect the telephone from the alarm system. The transistor circuit responds to the presence of the control signal by connecting the alarm to the telephone line when the control signal is present. An intrusion opens an intrusion switch, begins the magnetic tape player which, in turn, permits the modulated control signal to turn the dialing switch on and off and thereby dial a remote phone. The oral message is then delivered to the remote location.
|
