Other

William H Dittmer

Keith H Wycoff

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. The power saving circuit causes the signal processing circuits of the pager receiver to operate in a low power mode in which the signal processing circuits are deactivated for an extended period of time, such as for 256 seconds, when a received signal includes an inverted synchronizing signal following the last codeword transmitted, the signal processing circuits being maintained in the low power mode in response to a received signal which includes the preamble signal followed immediately by an inverted synchronizing signal.

Battery saving arrangement for selectively addressable, portable

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. A second optional connection may be made internally in the receiver so that a proper code will unsquelch the receiver for a certain time and thereafter place the receiver in condition to be unsquelched by just the carrier wave. Subsequent actuation of the push-button switch will cause the receiver to revert to its code-squelch mode. The receiver can manually be placed in the carrier-squelch mode by actuating the same switch for at least a certain time. The receiver further comprises a battery saver circuit which produces a pulsed supply voltage for the processor circuit, the decoder circuit and the audio circuit. While the correct first tone is being received, the battery saver circuit provides a continuous supply voltage to these various circuits, which voltage is maintained during the entirety of the code and for a time thereafter. When the second optional connection is made, as described above, the rate of the pulsed supply voltage produced after such time has passed will be increased. Alternately, if the push-button switch is operated, the receiver will be manually placed in the carrier-squelch mode, and the rate of the pulsed supply voltage will be increased. Subsequent operation of the push-button switch will reset the receiver to the code-squelch mode and cause the pulsed supply voltage to revert to its usual rate. A two-tone decoder circuit includes a normally operative channel for the first tone and a normally inoperative channel for the second tone. The first channel includes a frequency discriminator responsive to a first tone of predetermined frequency. The first channel also includes means to convert the first tone into a train of pulses. A delay circuit in the first channel produces a train of modified tone pulses commencing a first predetermined time after the start of detection of the first tone, to render ensuing circuitry nonresponsive to glitches (extraneous pulses such as noise and the like). An envelope detector produces an output pulse when tone pulses are absent for a second predetermined time. A latch is set by the first of the tone pulses and is reset by the output pulse. Accordingly, a tone signal is produced which commences a first predetermined time after the first tone starts and ends a second predetermined time after that tone ends. The first channel further includes a duration detector which responds to a tone signal of at least a predetermined duration to produce an enabling signal commencing with the termination of the first tone. The enabling signal is coupled to the second channel which has the same basic elements as the first channel, namely a frequency discriminator responsive to the second tone, means to convert the second tone into a train of pulses, a delay circuit, an envelope detector, a latch and a duration detector. The duration detector provides detected signals representative of the duration of such second tone. A control circuit produces one of a plurality of alerting tones having characteristics and durations corresponding to the detected signals. A gate circuit is rendered operative by a control signal from the control circuit to apply the alerting tone to the audio circuit. In the absence of such control signal, the output of the gate floats so as not to load the audio circuit while it is processing the intelligence signals. The first tone in the two-tone sequence may have one of two durations. A shorter first tone will enable the second channel as just described, while an even longer first tone bypasses the second channel to cause an alerting tone to be applied to the audio circuit. Such longer tone will similarly enable all receivers responsive to that same first tone to call them as a group. An optional connection may be made in the first channel to cause it to respond to a first tone of longer-than-normal duration to provide an output which also bypasses the second channel. This option enables ready conversion to a single tone receiver. The decoder further includes an oscillator and a chain of free-running, divide-by-two circuits to produce a plurality of clock frequencies. Each of the circuits described above includes one or more chains of resettable divide-by-two circuits connected to the clock. The timing functions in the receiver are performed by the clock and these resettable divide-ty-two circuits.

Selective call communication receiver

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.

Variable bandwidth filter

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. As soon as determination is made that the incoming signal does not have such character, the receiver is stepped to the next channel.

Signal absence detector

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. A tone signal of at least a predetermined duration produces an enabling signal commencing with the termination of the first tone. There is produced an alerting tone having characteristics corresponding to the duration of the second tone. In the absence of a control signal, the output of a gate that feeds the audio circuit floats so as not to be a load. A long first tone enables all receivers in the group. A multiple tone receiver is readily connected to a single tone receiver. The timing functions in the receiver are performed by the resettable divide-by-two circuits.

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.

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Lexington, NE, United States of America

William H Dittmer