Abstract: A receiver includes a receiving circuit for receiving an electromagnetic carrier wave modulated by a message signal, a detector ciruit for separating the message signal from the carrier wave, and an output circuit. The detector circuit has a Q ratio sufficiently low that the detectable band width is more than twice the modulation frequency change. The detector output signal has a noise voltage level when no carrier is present that is higher than the voltage of the message signal with a carrier present. An output circuit senses the level of the detector output signal and passes signals with a voltage level below a predetermined level and otherwise blocks the output signal. The filtering of the output circuit is sufficiently low that its response time is faster than a tenth of a second. The output circuit includes a noisy input related to the detector output and a reference input.

Abstract: A security system having one or more sending units for transmitting an electromagnetic signal representative of a condition such as fire, smoke, intrusion, battery condition, an emergency or other condition to a central receiving unit. Upon reception of an electromagnetic signal, the receiving unit provides an electromagnetic carrier detect signal to a microprocessor. A software timer within the microprocessor keeps track of the time over which the carrier is detected. If the carrier detection continues for a time longer than about 20 seconds, then a jamming indication signal is provided to one or more outputs. While the system is being jammed, alarms are ignored thus avoiding false alarms due to interference.

Abstract: A radio frequency (r-f) transmitter has an electric oscillator circuit for producing an oscillating r-f signal in an antenna. A feedback sub-circuit of the oscillator circuit includes a surface acoustic wave (SAW) resonator for stabilizing the oscillations. The feedback circuit has a Q of less than 12000. There is a modulation sub-circuit of the oscillator circuit which includes a voltage variable capacitor. The voltage variable capacitor responds to input voltage variations to modulate the capacitance of the feedback circuit, thereby modulating the frequency of the transmitter. A garage door opener system employing the transmitter is also disclosed.

Abstract: A center pivot irrigation machine having a swing arm for irrigating corner areas of a field. The swing arm has a steerable support tower which follows a buried cable to guide the swing arm into and out of the field corners. A double hinge connection between the main irrigation boom and the swing arm includes one hinge joint which accommodates pivoting of the swing arm and another hinge joint which controls the operation of the tower drive motors. A cam switch monitors the steering angle of the swing arm tower and turns the sprinklers of the swing tower on and off in accordance with the steering angle to achieve uniform water application. A secondary set of sprinklers on the main boom is deactivated and the entire machine is slowed when the steering angle indicates that the swing arm is covering a rapidly increasing area.

Abstract: A center pivot irrigation machine having a swing arm for irrigating corner areas of a field. The swing arm has a steerable support tower which follows a buried cable to guide the swing arm into and out of the field corners. A double hinge connection between the main irrigation boom and the swing arm includes one hinge joint which accommodates pivoting of the swing arm and another hinge joint which controls the operation of the tower drive motors. A cam switch monitors the steering angle of the swing arm tower and turns the sprinklers of the swing tower on and off in accordance with the steering angle to achieve uniform water application. A secondary set of sprinklers on the main boom is deactivated and the entire machine is slowed when the steering angle indicates that the swing arm is covering a rapidly increasing area.

Abstract: A center pivot irrigation machine having a swing arm for irrigating corner areas of a field. The swing arm has a steerable support tower which follows a buried cable to guide the swing arm into and out of the field corners. A double hinge connection between the main irrigation boom and the swing arm includes one hinge joint which accommodates pivoting of the swing arm and another hinge joint which controls the operation of the tower drive motors. A cam switch monitors the steering angle of the swing arm tower and turns the sprinklers of the swing tower on and off in accordance with the steering angle to achieve uniform water application. A secondary set of sprinklers on the main boom is deactivated and the entire machine is slowed when the steering angle indicates that the swing arm is covering a rapidly increasing area.

Abstract: A guidance system for a lateral move irrigation machine of the type having an elongate boom mounted on a plurality of motor driven towers which drive the boom along the field in a straight line path. A plurality of check points in the field are established by a series of magnetic and metallic elements placed in rows along the path of travel of the towers. The towers carry gradiometers or proximity switches which are sensitive to the elements and which deactivate the drive motors of the towers when the check points are reached. When all of the towers have reached the check points, the boom is properly aligned, and override circuits then activate the drive motors to resume movement of the machine.

Abstract: A device which controls the discharge of liquid from an elevated spray head according to the wind conditions. A wind sensor is mounted near the end of an irrigation boom or other elevated pipe. An end spray head for the boom is controlled by a motor driven valve. When the sensor detects wind along the boom above a selected velocity, a circuit is activated to operate the valve motor in a manner to turn the spray head off or on, depending on the wind direction. The circuit includes time delay relays which disregard sudden gusts of wind.