Intrinsically safe photo switch

The Pyott Boone Model 236IA Photo switch is designed as a general purpose, light controlled switch. The Photo Switch provides the ability to remotely control functions such as opening doors, throwing track switches, operating feeder-breakers controlling water sprays, and many others. The Photo Switch consist of a Control Unit and two Photo Sensors. Each Photo Sensor has 50 feet of 16/2 cable and a sensor housing extension that is used to reject ambient light.  These sensors are connected through barriers to the p.c. board.

The Model 236IA uses two Photo Sensors to detect the presence of light rays.  When light strikes either Sensor, a signal is sent to the Control Unit that energizes a  relay.  This relay will remain  energized until light strikes either Sensor a second time or the Control Unit times out. The Model 236IA Control Unit features a LOAD ON indicator. The UNIT TEST switch is used to test the p.c. board. The UNIT BYPASS switch allows manual operation of the unit.  The LOAD ON indicator ( green ) is illuminated when the relay is energized. 
Incorporated in the p.c. board is a timer feature.  To operate in the time-out mode, the toggle mode must be disabled (jumper off).  When the timer feature jumper is on both pins the  time-out feature is disabled.  When the jumper is removed (on one pin only), the timer feature is enabled.  Adjust the potentiometer to set the time-out delay.  The unit will automatically disengage the relay after the time interval set.  The time-out is variable from two seconds to three minutes.  For the toggle mode of operation, the jumper must be in place (connecting both pins). 

To operate, the time-out feature must be disabled (jumper on).  In this mode, the unit senses a light source and energizes the relay.  One of the sensors must sense the light source a second time to disengage the relay.  The light detection feature selects the reaction time to the light source.  With the jumper connected (covering both pins), the unit will respond to a fast pulse of light.  When the jumper is off one of the pins, it is in a slow detection mode.  The light must remain on the sensor for at least 1.5 seconds for the unit to respond to the light signal.  The SLOW position is used to prevent false activation of the unit.  A sensor housing extension is provided to reject surrounding ambient light.