Abstract: A two-way voice controlled communication system for use with a protective helmet. The communication system includes a transmitting circuit which is normally off, and which is voice actuated, and a receiving circuit which is normally on. The transmitting circuit includes a microphone and an electronic switch which turns the transmitting circuit on and the receiving circuit off in response to the presence of an output from the microphone, and turns the transmitting circuit off and the receiving circuit on substantially immediately in response to the absence of a microphone output. Thus the system approximates two-way real-time communication by permitting one user of the system to interrupt the speech of another user of the system. The system is designed primarily for far field communication, that is, omnidirectional communication where the spatial positioning of one communication system relative to a second communication system is essentially independent of the distance between the two systems.

Abstract: A control system for powering the direct current drive motor of an electric vehicle from a storage battery employs a semi-conductor switch to connect the battery to the motor. Speed control of the vehicle is achieved through operator control of an accelerator which provides an analog output voltage. A multi-vibrator provides a bi-valued output signal varying between 100% on time and 100% off time as a function of the accelerator output. The motor energizing switch is conditioned by this output and by the output of a circuit which compares the motor armature current to a reference value. The circuit includes protection elements so that the switch is opened when the armature current exceeds a preset maximum and is allowed to close again if the multivibrator is still in an "on" mode when the armature current decays below a lower preset value.

Abstract: An induction heating generator consists of a Hartley oscillator employing a tank circuit, including the induction heating coil, disposed in series with the emitter-collector circuit of the transistor. A bias circuit consisting of the parallel combination of a capacitor and diode is connected to the base and the feed-back voltage to the base is generated by a tickler coil. In the absence of oscillations the base is biased for class A operation and the resulting feed-back current charges the bias circuit to shift the operating point to class C operation. The bias voltage is decreased when the tank coil is loaded, lowering its impedance. This maintains stable operation of the oscillator independent of variations in the load. When the coupling between the load and the inductor is so great as to overload the oscillator, the bias circuit prevents oscillation.

Abstract: A control system for powering the direct current drive motor of an electric vehicle from a storage battery employs a semi-conductor switch to connect the battery to the motor. Speed control of the vehicle is achieved through operator control of an accelerator which provides an analog output voltage. A multi-vibrator provides a bi-valued output signal varying between 100% on time and 100% off time as a function of the accelerator output. The motor energizing switch is conditioned by this output and by the output of a circuit which compares the motor armature current to a reference value. The circuit includes protection elements so that the switch is opened when the armature current exceeds a preset maximum and is allowed to close again if the multivibrator is still in an "on" mode when the armature current decays below a lower preset value.