Abstract: A simplified and easily constructed device for loading and unloading a tape cartridge is disclosed. The device consists of a rotary member rotatably mounted on a chassis. The rotary member has a holder portion positioned for selectively engaging and disengaging a V-shaped notch in a tape cartridge in association with the rotational motion of the rotary member. The rotary member also has a responder portion positioned for being engaged by a cartridge upon insertion and rotating the holder portion into the V-shaped notch. A floating pin and a spring for biasing the pin into contact with a recess in the rotary member are used to restrain the rotational movement of the rotary member and assure a positive loading and unloading of the cartridge.

Abstract: A combined two (stereo) and four (quadraphonic) channel tape recorder is disclosed which can use both two and four channel eight track magnetic tape cartridges. The tape recorder includes a head positioning rotary body having four fixed rotary positions and a selection means for selecting two of these four fixed rotary positions when four channel (quadraphonic) operation is desired. The selection means comprises a rotary switch rotated in association with the rotation of the head positioning rotary body and an additional switch connected in series with the rotary switch and actuated by each rotation of the rotary body. Thus a single tape recorder capable of playing stereophonic and quadraphonic magnetic tape cartridges has been provided.

Abstract: An improved receiver voting system is disclosed in which the lowest noise audio signal produced by a number of different radio receivers is selected and coupled to a monitoring speaker. Each receiver receives signals from a transmitter and produces either corresponding audio signals or squelch indicating status tones which are then transmitted to a voting (selecting) control center by telephone communication lines. The voting control center then selects the unsquelched receiver audio signal having the lowest noise level and couples this signal to a monitoring speaker.The voting center indicates which receiver is supplying the selected signal and therefore identifies the most favorable receiver to transmitter signal path. Parallel squelch circuits in each receiver provide for the initial selection of the strongest received signal while preventing the existence of an irratating "squelch tail.

Abstract: A harmonic filter failure detection apparatus for use in a single sideband radio transmitter is disclosed. A first directional coupler measures the power delivered to the harmonic filter and a second directional coupler measures the power passed through the harmonic filter. The power measurements of the first and second directional couplers are then compared in a latch type comparator circuit and a control signal output is developed which indicates whether or not the harmonic filter is operating properly. The control signal output is used to shut down the single sideband transmitter when a filter failure has been detected.

Abstract: A microphone which consists of a speaker having a base resonant frequency, a suppression circuit for reducing the frequency response of the speaker at the base resonant frequency, and a high pass filter for reducing the base frequency response of the speaker is disclosed. The speaker creates electrical signals in response to sound waves received and the suppression apparatus reduces the relative magnitude of the electrical signals having frequencies substantially equal to the base resonant frequency of the speaker. The high pass filter reduces the magnitude of all electrical signals having frequencies below a predetermined frequency, and thus a desired microphone frequency response is obtained.A communications system which uses a receiver to drive a speaker in one mode of operation and uses the speaker as a microphone followed by a compensation network and a transmitter in another mode of operation is also disclosed.

Abstract: An improved gain antenna which is vertically mounted to a horizontal ground plane is disclosed. The gain antenna substantially consists of a radiating conductor having first and second ends and a centrally located feed point, and phasing apparatus electrically connected to the conductor for producing a predetermined current distribution. The phasing apparatus produce shortened out of phase current sections along the length of the conductor. Centrally feeding the gain antenna results in an improvement in the bandwidth and input impedance. The conductor consists of a linear section of coaxial cable which extends vertically from the horizontal ground plane to approximately the central feed point and a solid conductor rod which extends vertically upwardly from the central feed point. Current phasing apparatus having improved bandwidth and reactance characteristics are also described.

Abstract: A pager antenna system having two conductive containers which act as radiators and form a dipole antenna is disclosed. A metallic coil constructed of tubular material is positioned between the conductive containers and has a first end electrically connected to one of the containers. The tubular coil forms part of an antenna impedance matching network and also serves as a conduit for wires which interconnect circuit components located in each of the conductive containers. High frequency isolating chokes are connected in series with the interconnecting wires emerging from a second end of the tubular matching coil and prevent these wires from forming low impedance RF paths between the conductive containers. By making the RF impedance matching coil also serve as a conduit for low frequency interconnecting wires, fewer parts are required, the interconnecting wires are shielded from external influences, and low Q chokes can be used by connecting them across points which have a low RF impedance therebetween.

Abstract: A circuit for generating a temperature varying control voltage which is applied to a varactor diode to temperature compensate a crystal oscillator is disclosed. The circuit produces a substantially linear voltage versus temperature variation, including a point of inflection, in a middle temperature range, and a substantially non-linear voltage versus temperature variation in hot and cold temperature ranges. The control voltage versus temperature characteristic also undergoes a change in slope polarity in both the hot and cold temperature ranges. The temperature compensating circuit has a middle range circuit for independently creating the substantially linear variation in the middle temperature range, a cold range circuit operative below a predetermined temperature for creating the desired variation in the cold temperature range, and a hot temperature circuit operative above a predetermined temperature for creating the desired temperature variation in the hot temperature range.

Abstract: An oven having a thermistor controlled proportional heating system is compensated for ambient temperature variations by using a second thermistor sensing ambient temperature and connected in series with the control thermistor in an electrical bridge circuit. The control thermistor is mounted within the oven and substantially monitors the oven temperature while the ambient thermistor is located outside the oven and monitors ambient temperature. The electrical bridge circuit produces a temperature control error signal which is amplified and applied to a heater winding which is wrapped around the oven. The ambient thermistor produces a resistance variation in the electrical bridge circuit which modifies the temperature control signal such that a predetermined point inside the oven is held at a constant temperature regardless of any ambient temperature changes.

Abstract: A method and apparatus for a thermal printer head which uses individual heater elements as switching devices is disclosed. The printer head consists of an array of individual resistors each capable of causing a dot to print on thermally sensitive paper. The use of heater elements as switches reduces the total number of lead outs required for the printer head. A system that uses such a thermal printer head is also disclosed. The individual resistor heater elements have a voltage-current switching characteristic which enables them to be used as switching devices in addition to their function as heating elements.

Abstract: Apparatus for switching a silicon controlled rectifier (SCR) into an off state and maintaining it there is disclosed. The apparatus uses a diode and an inductor in series with the cathode of the SCR. The voltage developed across the diode is negatively applied across the gate to cathode electrodes to maintain the SCR in an off condition. The diode voltage is applied to the SCR electrodes by a switching transistor. An alternator regulator system which uses the SCR control apparatus is also disclosed.