Abstract: The antenna of a transceiver couples through a low pass filter to the input port of a high pass filter network. The high pass network is designed to reflect a very high impedance to its input port when its output port is at ground potential. The transmitter portion of the transceiver couples to the input port of the network with the receiver coupling to the network output port. A semiconductor diode couples from the output port to ground potential.In the receive mode the combination low pass and high pass filters couple received signals in the desired frequency band to the input of the receiver. Upon activation to the transmit mode the diode is forward biased whereby the network output port is taken to ground potential. In this mode the filter network effectively isolates the receiver from the transmitter.

Abstract: A fast forward cartridge tape player includes the conventional cartridge receiving cavity and cylindrical capstan. The capstan is rotatably driven about its vertically positioned longitudinal axis by a motor actuated flywheel, and it is located to forcibly engage the cartridge pressure roller on cartridge insertion into the cavity. Crescents, having a concave face, a convex face, and a vertical dimension are positioned to rotate about the capstan. The concave face encircles greater than 180.degree. of the capstan circumference while revealing a substantial arc on the capstan surface. The convex face is of predetermined curvature providing a desired fast forward speed/normal speed ratio. The vertical dimension of each crescent is fixed to allow each crescent access to the pressure roller. In the normal mode play a means decouples capstan rotation from the crescents and aligns the crescents to allow the pressure roller access to the revealed capstan surface.

Abstract: A rate one-half random error convolutional coding system corrects the theoretical limit of one error out of four successive bits. An information bit stream is processed through the system encoder which is comprised of a two-bit shift register and a modulo-2 adder. The encoder generates a parity bit formed by the modulo-2 summing of successive pairs of information bits, and produces a convolved transmission bit stream. The system decoder is the replica of the encoder in combination with a two-bit syndrome register, an AND gate, complementary feedback circuitry, and an output modulo-2 adder.Overall system performance is the simplest, fastest, and highest performing of all such systems known to date.

Abstract: A radio receiver includes a blanker circuit for muting the receiver in response to interfering noise signals. The invention contemplates a transistor switch which, when biased to its nonconducting state, inhibits blanker action. The transistor is biased to nonconduction when the receiver provided automatic gain control (AGC) level is below the threshold voltage of the transistor. An adjustment is provided for controlling the AGC level at which blanker inhibit is introduced. Temperature compensating circuitry maintains inhibit action response at the threshold voltage with changes in ambient temperature.

Abstract: The inventive counter is operable to divide an input signal by the sum of two binary numbers, A and B. Each number is stored in memory. These numbers are alternately preset into a binary counter which also receives the input signal. A logic gate monitors the counter output and changes state when the number previously preset in the counter equals the accumulated count. The gate state transition is used to preset the counter with the alternate stored number. Thus, the process continues whereby the output from the logic gate represents the input signal divided by the sum of A and B.

Abstract: A fast forward drive for a cartridge tape player comprises upper and lower crescents which increase the effective capstan diameter in the fast forward mode. At normal playing speed the crescents index with respect to a received tape cartridge such that the capstan's surface forcibly engages the cartridge's pressure roller.When the fast forward mode is desired a clutch couples the upper crescent to the capstan for rotation therewith. Rotational drive of the upper crescent is coupled to the lower crescent, at a predetermined phasing relationship, through a pin and trough arrangement, whereby fast forward is effected. On return to the normal play speed the upper crescent is fixedly indexed, resulting in a decreased lower crescent rotational drive and thus an increased chance of improper lower crescent alignment. To promote lower crescent indexing a second spring clutch is mounted on the capstan between the lower crescent and the housing which actively drives the lower crescent to its indexed position.

Abstract: The output from a peak detector of a conventional radio receiver includes a recovered audio signal and a DC level. The disclosed noise limiter processes the detector output through both low pass and high pass filters. The low pass filter produces a DC signal representative of both the detector DC level and the recovered audio signal level. The high pass filter passes only the recovered audio signal. A semiconductor diode connects between the filter outputs, and the output of the noise limiter. For peak detector levels at, or below the 100% modulation level the diode is forward biased and passes the audio signal to the noise limiter output for further receiver processing. Peak detector levels exceeding 100% modulation, such as noise, reverse bias the diode whereby the audio signal is blocked from subsequent receiver stages.

Abstract: A radio transceiver includes means to switch from the transmit to the receive mode. The disclosed squelch circuit operates in the receive mode to mute and unmute the receiver at different received signal levels to prevent undesirable muting during signal fading conditions. The squelch also provides a means to mute the receiver for a sufficient period allowing switching transients to die out after the transceiver has been switched from the transmit to the receive mode.

Abstract: A resistor is inserted between the audio signal and the primary winding of a conventional modulating transformer used in an amplitude modulated transmitter. The value of the resistor is selected to limit the peak signals into the transformer thereby limiting the peak instantaneous index of modulation to less than 100 percent.A capacitor, coupled to the transformers secondary winding, forms a low pass filter with the impedance of the resistor as transformed by the turns ratio of the transformer. The resulting low pass filter attenuates undesired harmonics.

Abstract: A two-way FM radio transmitter-receiver operates on a single channel and automatically samples the channel during transmissions to sense the presence of a carrier wave. The transmitter is actuated by use of a transmit key which starts timing means to produce a time interval, and at the end of the time interval a sample generator is actuated for a very short time period to turn off the transmitter, disconnect the antenna from the transmitter, and connect the antenna to the receiver. A detector coupled to the squelch circuit of the receiver at the transmitting station detects the presence of a carrier wave on the channel, and the detector output produced in response to a carrier wave acts to hold the transmitter off and allow the receiver to reproduce the received wave. When the transmitter is turned off for the short time period, the absence of the carrier will cause the FM receiver at the receiving station to produce a burst of noise.

Abstract: A reversible continuous loop cartridge includes a conventional front accessible pressure roller drive. A first pulley is affixed to, and rotatable with the roller. A second pulley is coupled through a one way clutch to the cartridge hub. An O ring interlocks the two pulleys, whose diameters are in a predetermined ratio. When driven in the forward direction the roller, and pulley rotate but the clutch decouples the hub whereby the tape is driven in the well known manner. When reversely driven the clutch engages such that the roller, pulleys, and hub rotate. The hub drive assures proper reverse operation of the continuous loop tape.A fast forward cartridge tape player includes the conventional cartridge receiving cavity and cylindrical capstan. The capstan is rotatably driven about its vertically positioned longitudinal axis by a motor actuated flywheel, and it is located to forcibly engage the cartridge pressure roller on cartridge insertion into the cavity.

Abstract: A unique printer head employs a plurality of bimorph benders to drive a wire matrix. The benders are of the circular, high power type, having centrally located coupling washers. A housing supports the benders which are stackably mounted therein such that the washer openings form a central cavity which is aligned with an opening in the housing. Each wire couples to a corresponding bender to be ballistically driven thereby. The wires are routed through the central cavity and wire guides for actuation out the housing opening.Because of the high efficiency of the bimorph bender drivers, the improved printer head has reduced size and weight, while maintaining a high reliability.

Abstract: The coupler inserts in an RF transmission line and produces a pair of DC signals whose level is representative of the magnitude of forward or reverse power flow therethrough.Power flow is sensed via a pair of non resonant loops, each of which is terminated and oriented such that AC signals, whose amplitudes correspond to the forward or reverse power flow magnitude, are produced. Since the RF signals produced by the loops are dependent on the RF power flow frequency, unique circuitry processes the RF signals and compensates for this frequency dependence whereby the processed AC signals are substantially frequency independent.Also disclosed are improved rectification circuitry, and a means to compensate the coupler against error due to thermal drift of coupler components.

Abstract: A controllable oscillator is maintained at a center frequency f.sub.o by the inventive system. The oscillator signal is directly coupled to one input of a diode detector via a first path, and is alternately coupled, at a clock signal rate, to the second detector input via second or third paths. The second path has a selected transfer characteristic such that when it passes the oscillator signal the diode detector output is at a null. The third path includes a resonator whereby the oscillator signal passed therethrough results in a null at the detector output only when the oscillator is tuned to f.sub.o. The diode detector output is then phase detected with the clock signal thus producing an output correction signal which, when integrated, is fed back to the oscillator for precise control thereof. Since the system correction is dependent solely on an AC signal, errors due to the DC characteristics of the components, e.g. the detector diodes, may be eliminated.

Abstract: A system for processing a digital information bit stream and generating a data bit stream. The processing includes convolutional burst error correction encoding which is capable of correcting burst errors of length 2B, where B is any positive integer. Inherent in such systems are the requirements of 2B and 5B zero level bits at the beginning, and end, respectively, of the data bit stream. The processing further includes encoding n sync bits at the beginning of the data bit stream.The improvement includes encoder apparatus for replacing the 2B zero bits with the n sync bits; and, decoder apparatus for detecting a threshold number of sync bits and, in response thereto, replacing each sync bit with a zero bit. This improvement significantly reduces the number of bits otherwise required in the data bit stream.

Abstract: An improved detection arrangement for detecting the presence of a given tone in a received input signal. A reference generator, in the form of a reference clock and a programmable divider, produces a first reference frequency, equal to the frequency of the tone, and at an arbitrary phase angle thereto. A second generator output is in quadrature to the first. Each reference signal is product detected with the input signal via exclusive OR gates.A unique digital low pass filter, operating in a time multiplex mode, receives the gate outputs, removes all high frequency components therefrom, and produces pairs of output binary number encoded signals, each of which is representative of a vector component of a detected tone. Threshold detector circuitry monitors the outputs indicating an above threshold condition at its output in response to predetermined combinations of the binary numbers. The combinations represent all input vectors whose resultant absolute magnitude exceeds a chosen threshold.

Abstract: A digital system controls ignition dwell for an internal combustion engine. Dwell time is maintained constant, thus assuring a constant high level ignition spark, over the entire active RPM range of the engine. In addition, the system compensates for temperature and aging induced changes in the ignition components.In operation, one sensor generates pulses representative of engine angular position while a second produces ignition pulses. An angle counter stores the number of position pulses generated thereby creating a count representative of engine position. A speed counter stores the number of position pulses generated for a clock interval, producing a count representative of engine speed. Dwell time is initiated at a predetermined relationship between the counter outputs which assures a constant dwell time. Feedback circuitry monitors current through the ignition coil and alters the clock interval to compensate for ignition component changes.

Abstract: A fast forward drive for a cartridge tape player comprises upper and lower crescents which increase the effective capstan diameter in the fast forward mode. At normal playing speed the crescents index with respect to a received tape cartridge such that the capstan's surface forcibly engages the cartridge's pressure roller.When the fast forward mode is desired a clutch couples the upper crescent to the capstan for rotation therewith. Rotational drive of the upper crescent is coupled to the lower crescent, at a predetermined phasing relationship, through a pin and trough arrangement, whereby fast forward is effected. On return to the normal play speed the upper crescent is fixedly indexed, resulting in a decreased lower crescent rotational drive and thus an increased chance of improper lower crescent alignment.