Abstract: A wireless security system in which a sensor for detecting a security violation is provided with a radio frequency transmitter adapted to excite the receiver of a control unit at a different location, the transmitter of the sensor radiating a signal responsive to the occurrence of a security violation. The sensor also having means to periodically excite the transmitter after the lapse of a period of time to indicate that the sensor is in proper working order, that period varying randomly. The control unit is provided with a memory and stores responses to the random signals, and at intervals long with respect to the random periods, samples the memory. The control unit responds to the absense of a stored response from the transmissions of the sensor.In a preferred construction, a plurality of sensors are employed with a single control unit, each of the sensors radiating a unique encoded signal.

Abstract: A biochemical oxygen demand measuring device which utilizes the decrease in pressure in an air space above the sample under measurement in a sealed reaction vessel to actuate an oxygen generator which utilizes an electrolysis cell communicating with the reaction vessel. The quantity of oxygen supplied by the oxygen generator is a measurement of the biochemical oxygen demand and is proportional to the quantity of electricity used in the electrolysis cell. Electrical pulses in a chain of constant amplitude and constant duration are applied to the electrolysis cell and the chain of pulses is interrupted by means responsive to the pressure in the reaction vessel to maintain the pressure in the reaction vessel constant. A counter is employed to count the pulses over a period of time as a measurement of the oxygen taken up by the reaction in the pressure vessel. A barometric correction device is employed with a sensing electrode in the electrolysis cell to control the pulses of electrical energy.

Abstract: A security system in which fire or intrusion signals may be impressed on a first and a second monostable oscillator connected in timing circuits, the first monostable oscillator producing an output for a first limited time period to excite an alarm, and coincidently in time a second monostable oscillator producing an output of shorter second time period for delaying actuation of the alarm to permit the operator to deactivate the unit prior to actuation of the alarm, each of the monostable oscillators using an integrated circuit and being reset by application of power to the unit and during function key switch position change. The fire channel has top priority over any other functional characteristics of the master control.