Other

International Medical Electronics Ltd.

Terra Corporation

Noel A Rogers

A diathermy apparatus has a power circuit operative at a selected, fixed frequency. An applicator head, for providing therapeutic treatment, has an irradiating portion. A transmission line connects the power circuit and applicator head, and is of a length so that, at the frequency, a selected minimum power is delivered to the applicator head when unloaded, the length further being such that a selected maximum amount of power is delivered to the applicator head when it is in a loaded position in close proximity to a patient load. The diathermy apparatus also includes a cabinet and portable base, wherein the portable base mounts the applicator head, and provides a carriage for the cabinet. The applicator head has an internal fan for cooling components of the applicator head. A display is provided for displaying the actual power consumed by the patient load. A processor independently controls the pulse modulator and power circuit in digital increments on a selected scale.

Diathermy apparatus with automatic tuning for applicator head

An improved aircraft marker beacon receiving and indicating system is provided, which automatically responds to the amplitude of the received signals to provide reduced sensitivity and muting of audio output after initial sensing and indication of proximity to the beacon and during a timed period of passing over the beacon in closest proximity thereto. The improved system employs an electrically controllable radio frequency attenuator between the antenna and the input of the receiver. The attenuator is controlled by a control voltage of predetermined duration from a trigger actuated, timed control signal generator. The control signal generator is triggered by direct current trigger pulse signals from an audio frequency peak detector. The peak detector derives its input from an operational amplifier coupled to receive audio frequency signals from the demodulator output of the tuner portion of the receiver. The control voltage from the timed control signal generator is applied to the reference input terminal of the operational amplifier to mute the loudspeaker or headphones coupled with the output of the operational amplifier, as well as to the attenuator to reduce the sensitivity of the receiver.

Automatic sensitivity adjustment and audio muting for aircraft marker

A method and apparatus for simultaneously operating two diathermy treatment heads in close proximity without interference caused by phase and frequency differences. Each diathermy head has a drive circuit powered by a master oscillator providing RF energy. Each head can be used alone with RF drive from its own oscillator. When the heads are to be used in close proximity, they are coupled by coaxial cable, and one oscillator is automatically disabled to permit the other oscillator to furnish the RF drive for both systems. The RF drive is then coherent in phase and frequency in both systems, so the two diathermy heads do not 'fight' each other.

Method and apparatus for operating dual diathermy applicator heads in

Disclosed is an electronic channel selector comprising a plurality of diodes in series with a plurality of crystals, each diode/crystal connection defining one channel of the ten channel crystal-controlled oscillator. Non-enabled diodes are maintained in a reverse bias condition, preventing the associated crystal from oscillating in the oscillation circuit. The diode corresponding to the selected channel is forward biased into conduction permitting the associated crystal to control the oscillator circuitry providing the desired frequency output. When the selected diode is forward biased and begins conducting current, it conducts current through a path which provides a tuning voltage which may advantageously be utilized in a transmitter exciter filter or receiver preselector. A binary switch is manually set for the desired channel and produces a binary coded output. A binary-to-decimal decoder provides a single enabling output which is determined by the binary code supplied from the binary switch. The decoder output is inverted and forward biases the diode corresponding to the selected channel.

Electronic channel selector

An improved frequency control system for radio apparatus is provided, which is especially advantageous for employment in portable, battery powered, multichannel, radio transceivers.The system involves both individual and combinational type improvements relating to the constructional and operational aspects of transceiver equipment. Some salient features of the system include digital frequency synthesizer circuitry having a frequency and phase locked loop employing a voltage controlled oscillator, out-of-band selection detecting and transmit inhibit signal generating circuitry, and filtering and amplifying circuitry employing voltage controlled tuning and improved wide-band inter-stage coupling for supplying frequency controlling signals for both a receiver and a transmitter from a common excitation source.

Frequency control system for radio apparatus employing filter amplifier

A low level modulation circuit for use in a radio transmitter obviates the needs for an audio transformer device heretofore required for high signal level modulation of the final stages of a multistage radio frequency amplifier by modulating an initial amplifier stage using a conditioned, low level modulation signal, but yet eliminates additional distortion and noise imposed upon the modulated audio signal by the initial and intermediate amplification stages, through the use of a single, negative feedback circuit. The feedback circuit novelly employs a directional wave coupling device and envelope detection circuitry for deriving signal information from the modulated radio frequency carrier wave just prior to radio transmission of the latter, and functions to combine the derived signal information with the output of a modulating signal source in order to produce a conditioned, low level modulating signal input to the initial amplification stage which modulates the transmitter in a manner to maintain the radio frequency power output of the transmitter at a nearly constant level in spite of variations in supply voltage or amplifier gain, while also reducing noise and distortion in the modulating portion of the transmitted radio output wave. The effects of reflected waves on the antenna line are also sensed by the feedback circuit which uses a shunting diode to drain energy from the initial radio frequency amplification stage and prevent overdriving or burnout of the radio frequency amplifier in the event that abnormally high reflected waves are sensed.

Low level modulation system for a radio transmitter

Especially simple structure for an electrical transformer device provides cost effective fabrication thereof and offers improved operating performance particularly in a radio transmitter circuit for coupling high levels of radio frequency energy from the output of a radio frequency amplifier to an antenna system. One winding of the transformer is formed from a single, unitary, tubular member arranged into a U-shaped configuration which includes a pair of spaced sets of openings therein for the two-fold purpose of allowing efficient threading of a secondary winding therewithin and to improve air cooling characteristics of the device. A second winding comprises a wire passed through the interior of the tubular member, and a number of cylindrically shaped magnetic elements are sleeved over the tubular member to enhance the mutual inductive coupling between the windings. A circuit board having a cut-out zone therethrough is especially adapted to have the transformer device mounted thereon in an essentially flat position juxtaposed over the cut-out zone to provide maximum convection and conduction cooling of the transformer and thereby significantly increase the power handling capabilities of the device.

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Shawnee Mission, KS, United States of America

Noel A Rogers