| 摘要 |
<p>The invention provides an alarm panel connected to a telephone line. The alarm panel comprises a microprocessor connected to a circuit which operates in two states: passive and active. In the passive state, the alarm panel monitors the line for a ring signal and tests the integrity of the telephone line. In the active state, the alarm panel seizes the telephone line and provides full bi-directional communication with a receiver through the telephone line. The circuit is designed such that the individual subcircuits for each state operate independently of each other and can be modified to meet various regulatory requirements without affecting the other circuits. The circuit draws low current in the passive state. Finally, the circuit is separated from the microprocessor using only 2 or 3 optocouplers,</p> |
