Abstract: The accuracy of a required tone set, digitally synthesized by a microprocessor, is improved beyond the theoretical limit of the microprocessor circuitry by producing each tone at a frequency which is a sub-multiple of the desired frequency, then multiplying to provide the desired frequency. With the addition of a multiplier such as a doubler, a better choice of oscillator frequency becomes possible which further increases the tone frequency accuracy. The microprocessor can also reduce the start up time and the time between tones, eliminating delays in transmitting a series of coded tones.

Abstract: A broadband isolator design wherein the amount of insertion loss may be traded for bandwidth and possibly reduced circuit complexity. The isolator may employ two windings or conductors with the neutralizing element connected across the input-output terminals, or may have a third winding placed to bisect the angle between the other windings and the neutralizing element coupled across this third winding. The angle between the windings and the isolator interconnection determine the specific bandwidth and insertion loss.

Abstract: An access panel as for a small apparatus housing has a pivot pin with retracting ends for cooperating with a fixed point socket during normal operation. Excess force causes the pivot pin to translate onto a camming surface, which leads to the outer surface of the housing whereby the pin ends retract, and the door is released without damage.

Abstract: A completely flexible dipole antenna is formed from coaxial cable having a braided wire core with skirt also formed of shielding over a flexible sleeve. A coil spring which is not electrically active supports the antenna above the connector. A non-wearing female connector utilizes a flexible conductive elastomer contact contained within an insulating body.

Abstract: An improved AM stereo receiver for receiving broadcast signal having the form (1+L+R)cos(.omega..sub.c t+.phi.) where .phi. is arc tan(L-R)/(1+L+R). The sum signal (L+R) is demodulated in an envelope detector and coupled to a matrix. The uncorrected difference signal is demodulated in a synchronous detector, a corrector circuit derives the correction factor, and a divider circuit provides the corrected difference signal. During tuning, and until a PLL is locked on the carrier frequency, the receiver is locked into the monophonic mode and tuned on the monophonic signal. When the PLL locks, the difference signal is coupled through to the matrix for stereophonic mode operation.

Abstract: A system for the transmission and reception of two program signals L and R on a single channel by means of a compatible SSB AM stereophonic signal having the form (1+L+R)cos(.omega..sub.c t+.phi.) where .phi. is arc sin{[(L-R)/.pi./2] [1+(L +R)/2] / (1+L + R)}. The system is also applicable to transmission of one program signal on one set of sidebands.

Abstract: A CSSB system for AM stereo provides both second and third order sideband correction in the transmitted signal for reduction of distortion at the receivers. Sum and difference signals are derived from two audio program signals (L and R) and shifted in phase 90.degree. with respect to each other. The carriers is then phase modulated with the ratio of these two signals and amplitude modulated with the sum signal.

Abstract: An AM receiver for utilizing a broadcast signal of the form (1+L+R) cos (.omega..sub.c t+.phi.) separates the L and R signals by utilizing phase detection and matrixing. Distortion is either eliminated with non-linear amplification or reduced with partial matrixing.

Abstract: The cosine correction factor of a receiver for compatible AM stereo reception is controlled by the amount of high frequency energy present in the demodulated signal. Large amounts of such energy indicate a low signal-to-noise ratio and cosine correction under such conditions is then not desirable. During periods of excessive high frequency energy, a filter circuit output causes a switching circuit to remove the derived cosine correction factor and cause division of the demodulated signal by a factor of one instead.

Abstract: A base station encoder is connected to a decoder terminal and paging transmitter by means of a single voice-pair telephone line link. Automatic operations reduce operator fatigue and operating costs. Digital, tone-keyed gain controls automatically compensate for line losses. All dialing, including long distance and overseas calls, and station identification are done automatically.

Abstract: A current-mode output stage for a digital phase detector has its output current magnitude controllable, with the output polarity determined by the phase detector. Either two or three output states can be provided.

Abstract: An AM receiver for receiving a compatible stereo signal and requiring a dynamic correction factor prevents the introduction of a false phase reference signal by limiting and filtering the signal going into the oscillator of the PLL which provides the correction reference signal.

Abstract: A dual wound stator for a multiphase alternator operating at varying speeds and supplying rectified current at constant voltage with variable output. By combining windings having many turns of smaller wire with windings having fewer turns of larger wire, a compound curve of output is obtained, combing low cut-in speed with high maximum output and increased efficiency.

Abstract: A read-out of eight distinct function codes is obtained in a pager or similar device having a single two-word address code plug by creating a second, but dependent, address within the pager and transmitting one of eight possible variants of the two words of the two address codes and their complements. Two code plugs may also be used to provide two addresses with four function codes associated with each. Upon receipt of a coded address, the user is alerted, and the function code is stored in a write-over memory, available to be read-out on command unitl a new code is received. The memory can also be erased manually as desired. Display segments are scanned in sequence to conserve power, and a status check of the segments is provided at each power turn-on. Power status indication is also provided, at turn-on and at "read" command, utilizing both audio alert channels and the visual display elements.

Abstract: An improved mounting arrangement and method of assembly provides for mounting parts on both chassis and board, then mating the two before soldering by means of a twist-tab-and-slot arrangement. The conformation and dimensions of the tab and slot prevent warpage during soldering, enabling the use of the chassis as a board carrier in the wave soldering process.

Abstract: In an AM broadcast transmitter, an infrasonic tone is added to the difference channel of a compatible AM stereo system to provide a stereo presence signal. In a stereophonic receiver, the corrected output of a synchronous detector in the difference signal channel is coupled to an infrasonic detector for control of a mono/stereo mode switch and a stereo presence indicator. When the received signal is weak, the infrasonic tone is effectively stronger, because the phase angle is increased. Since the s/n ratio is proportional to the phase angle, the stereo presence signal is self-adjusting. The mode switch and indicator are enabled for all values of L and R. The infrasonic tone could also be removed from the transmitted signal whenever the difference signal goes above a predetermined level during stereo broadcasting, in which case a comparator at the receiver would enable the mode switch and indicator upon detection of either a difference signal or the infrasonic tone.

Abstract: A signal level controlled switching circuit removes the stereo correction factor in a compatible AM stereo receiver when the received signal level is low enough to allow signal degradation due to noise affecting the correction factor. The switching circuit can operate on either an instantaneous or an average signal level.

Abstract: Synchronization for data sampling pulses in a two-way alphanumeric data terminal is provided by utilization of signals present in the page address decoder circuitry. Microprocessor power-up timing is also obtained from the same signals.

Abstract: A container for a product serves to protect the product during shipping and storage, then opens to display the product. A bridge member attached to the inner walls of the container retains the product on a planar surface which is centrally located within the container in the protect mode and is elevated above the container in the display mode. A magnetic latch within the walls of the container holds the container in the display mode.

Abstract: A PNP/NPN complementary pair of common emitter connected output transistors are driven by separate differential amplifiers having unity feedback and biasing to prevent simultaneous operation. Only a single battery supply is required.