| 摘要 |
<p>A burglar alarm network protects a string of separated objects or locations, which depends on vibration prone contacts mounted at each location changing the current in the common connecting line when a disturbance occurs. The network uses photodiode series elements and optical coupling, instead of resistance alone, which result in tolerance problems over an extended string of objects. A number vibration prone contacts (9, 10) are connected in series with an equal number of photodiodes (12, 13, 14) which activate light sensitive transistors (15, 16,17) either in a separate line (18, 19) or alternatively in the same line (20). Four such networks are connected in a bridge array (24, 37) with photodiode (25, 26) monitoring of the imbalance current. If imbalance occurs due to a disturbance, a photosensitive amplifier pair (27, 28), logic network, and photodiode (35) alarm signals are activated.</p> |
