| 摘要 |
The present invention includes a continuous optical fiber secured to the movable control member and a connector unit which transmits and detects a light signal at opposite ends of the optical fiber and converts the detected light signal into an electrical signal. More specifically the present invention also includes apparatus for allowing authorized movement of the control member as well as means for detecting unauthorized movement of the control member. A preferred embodiment includes an optical fiber that is adapted to be secured to a movable control member of a valve and secured at each end to respective terminals on a connector unit. The length of the loop, optical fiber, and the position of the terminals and connector until are selected so that moving the movable control member of the valve interrupts the light path provided by optical fiber between the terminals to which the ends of the fiber are attached. A light source and a light detector circuit are located near the valve being monitored, and any interruption of the light path between this emitter and detector will produce an alarm signal. The alarm signal continues until that alarm signal is reset at a control panel. A preferred embodiment encodes the light provided by the light source to provide tamper-proof operation. In a particular embodiment, circuitry are provided for transmitting, detecting and converting pulses of light into electrical signals and for processing the electrical signals. Circuitry is also provided that distinguishes among electrical signals representative of the detected light pulses and the absence of detected pulses due to removal or breakage of an optical fiber.
|
