Abstract: A pager operated control unit has input terminals of the control circuit are connected to the battery terminals of the pager and power is supplied to the pager receiver from the control circuit. Pager generated pulses are detected by the detection of changes in current drawn by the pager receiver. The control unit includes a pair of capacitors which are alternately charged under the control of a flip-flop in response to bursts of pulses generated by a pager receiver. An output relay is operated to one state when the charges on the two capacitors substantially equal, indicating the receipt of a burst of pulses of equal duration, and operated to another state when the capacitors have unequal charges, indicating the receipt of a burst of pulses of unequal duration.

Abstract: A volume control device is inserted in the circuit between the output of a sound system amplifier and a speaker. The volume control device measures ambient noise in the music environment and adjusts the power transferred to the speaker, such that the output volume of the speaker increases and decreases with changes in the ambient noise. A variable throughput current device, such as a thermistor or a transistor, is connected in the speaker circuit to control a power transfer to the speaker. A comparator compares the output of an ambient noise detector with the signal applied to the speaker and the variable throughput current device is adjusted in accordance with the compared signals. A level detect circuit serves to maintain the speaker volume at a preset level when the amplifier output drops below a predefined signal level. The speaker may be provided with a sensing coil generating an output signal representative of the level of ambient noise in the vicinity of the speaker.

Abstract: Motion is detected from a surveillance monitor by means of a photosensor attached to the monitor screen and an electric circuit connected to the sensor which generates an alarm signal in response to changes in the level of an electric output signal generated by the sensor. The sensor is housed within a suction cup which is readily attached to any part of the screen and is readily movable to any desired area of the screen to be monitored for motion. The electric circuit includes comparators which detect changes in light intensity greater than a predetermined magnitude defined by a window about a preselected voltage level. The circuit includes an operational amplifier and a transistor connected to the output of the sensor and the circuit provides an effective impedance equal to the impedance of the sensing device at various levels of intensity such that the reference voltage level, for detection purposes, is the same at all levels of steady state light intensity.