Abstract: A pager receiver for receiving signals transmitted in the POCSAG code format which includes a preamble signal followed by at least one batch, the pager receiver including a preamble absence detector circuit for detecting whether or not a received signal includes the preamble and a power saving circuit responsive to the preamble absence detector circuit for deactivating signal processing circuits of the pager receiver as soon as detection is made that the received signal does not include the preamble signal.

Abstract: A hunting arrow tracking system includes a tubular housing removably connectable to an arrow shaft and enclosing a battery-powered transmitter. The batteries are disposed in a container in the housing which is spring biased against a piezoceramic transducer which generates a trigger signal in response to longitudinal acceleration or deceleration of the arrow to set a latch for connecting the battery to the transmitter, thereby causing it to transmit a low duty cycle pulsed signal. The transmitter is connected to a strip antenna which extends the length of the arrow shaft and is adhesively secured to the outer surface thereof. A directional receiver receives the transmitted signal and indicates the direction from which it is being received. The latch can be reset by passing a magnet over the arrow to activate a reed switch.

Abstract: There is disclosed an encoder comprising means for generating a plurality of tones with every other tone being in a first bank and the remaining tones being in a second bank. The tones are sequentially combined into a code in which every other tone is from the first bank and the rest of the code tones are from the second bank.

Abstract: The receiver comprises a processor circuit which receives and processes a modulated carrier wave. The modulation is a code consisting of a single tone or a sequence of tones, followed by intelligence signals. The processor circuit separates the code and the intelligence signals from the carrier wave. The receiver also comprises a decoder circuit responsive to a given code to provide an enabling signal. An audio circuit is rendered operative by the enabling signal so that it can process the ensuing intelligence signals. The receiver has a push-button switch which can be actuated at any time to monitor the channel. Such switch is associated with a timer and an electronic switch.A first optional connection may be made internally in the receiver, whereby actuations of the push-button switch places the receiver in a monitor mode so that it will be continuously on. Subsequent actuation of the switch will cause the receiver to revert to its tone-squelch mode.

Abstract: The filter has a fixed Q and is coupled to a source of AC signals. A source of pulses is applied to a variable-voltage circuit, the circuit being responsive to each pulse to produce a threshold voltage which varies from a first value toward a second value. A comparator circuit has one input coupled to the filter and a second input coupled to the variable voltage circuit. The comparator produces a signal for a duration related to the time the amplitude of an AC signal from the filter is at least equal to the threshold voltage.

Abstract: The signal absence detector controls an operator circuit which periodically provides an operator signal to render the processor circuit in a communication receiver operative. The absence detector responds to a processed signal which is not of a predetermined character to terminate the operator signal. In one form of the invention, the operator circuit is a battery saver which intermittently provides a supply voltage. When the incoming signal is of the predetermined character, the supply voltage continues. The absence detector terminates the supply voltage when it is determined that the incoming signal does not have that character. In another form of the invention, the absence detector is employed in a scanning receiver, in which case the operator circuit steps the receiver between the various channels. The receiver will remain tuned to a channel as long as the incoming signal may be of the predetermined character.

Abstract: A decoder circuit responds to a given code to provide an enabling signal for rendering an audio circuit operative. A push-button switch actuatable to monitor the channel is associated with timer and electronic switch.One connection places the receiver in either a monitor mode or a tone-squelch mode. A second connection places the receiver in condition to be unsquelched manually or by the carrier wave or by the proper code. The battery saver provides a continuous supply voltage during the first tone, the entirety of the code and for a time thereafter. The rate of the pulsed supply voltage produced after such time will be increased. Alternately, the receiver can be placed in the carrier-squelch mode. The receiver can be reset to the code-squelch mode and cause the pulsed supply voltage to revert to its usual rate. After the start of detection, pulses render ensuing circuitry nonresponsive to glitches.

Abstract: A memory device stores signals representative of a predetermined number of words constituting a given code. When and only when all the words have been received, a release signal causes the stored signals to be released to a device that displays or otherwise furnishes the information contained in the code. If more or less than the predetermined number of words is received by the decoder, a release signal is not generated.

Abstract: The encoder in such system generates a sequence of tones in which every other tone is selected from a first group of tones in one band of frequencies, and the remaining tones in the sequence are selected from a second group of tones in another band of frequencies. The tones in the second group are respectively harmonically related to the tones in the first group, such as having frequencies double the respective frequencies of the tones in such second group. The tones are generated by an oscillator in the encoder, every other tone being multiplied by 1/2, for example. Circuitry, coupled to the oscillator and to the multiplier, alternately delivers the divided and undivided tones, to create the afore-mentioned sequence of tones.The oscillator has associated therewith a switchable impedance, predetermined amounts of which are sequentially switched into the oscillator to cause it to produce the sequence of tones.

Abstract: The receiver includes a decoder responsive to certain characteristics of a coded signal, such as the frequency of tones, for producing a decoded signal indicative of second characteristics of the coded signal, such as the durations of the tones. A duration detector is responsive to the decoded signal to provide a detected signal having properties indicative of the tone duration. A utilization circuit is coupled to the detector and is operated in accordance with the properties of the detected signal. The utilization circuit may be an annunciator which produces an audible or visual alerting signal, or it may express digital information, or it may be a system which is to be remotely controlled. Such receiver may be one in a system of various groups of receivers which can be contacted simultaneously if desired.

Abstract: In one aspect, the circuit has a first impedance element which preferably is in the form of a tapped inductor with a plurality of taps thereon, and a second impedance element which preferably is in the form of a capacitor. One terminal of the capacitor is connected to a terminal of the inductor, the other terminal of the capacitor is movably connected to a selected one of the taps. The circuit is tuned to a resonant frequency determined by the value of the capacitor and the value of inductance associated with the selected tap. The taps are located on the inductor to cause each resonant frequency to be a substantially fixed percentage greater than the next lower one of the resonant frequencies. In one embodiment, a connector plug is provided, having a first portion with a terminal connected to the capacitor; a second portion with terminals connected to the taps on the inductor; and a third portion matable with the second and third portions.

Abstract: A tone control circuit is in a receiver adapted to respond to a sequence of control tones alternately selected from a first group of tones in a first band of frequencies and a second group of tones in a second band of frequencies, wherein the two bands are separated by an intermediate band and wherein the time duration of the gap between adjacent tones in the sequence of tones is substantially zero, the tone control circuit including a filter device which is tuned to the frequencies of the control tones as they are received, a plurality of AND circuits corresponding in number to the control tones and respectively having one input coupled to the filter device and another input coupled to the preceding AND circuit so that each AND circuit is operative to produce an output only in the presence of a tone being passed by the filter and an output signal from the preceding AND circuit, the filter device being tuneable either manually or electronically via the outlet signals from the AND circuits.