Abstract: An error checking circuit is provided for a digital transmission system having a dual, redundant, bus structure. The error checking circuit generates a two rail logic output having complementary states in the absence of an error, and non-complementary states in response to an error on the buses. The circuit is also self-checking in that internal failures are transmitted to the output as an error indication. The circuit is actively exercised in the absence of an error to prevent silent failures. The circuit can identify which of the buses has failed, for the most common types of failures.

Abstract: A phase locked loop (10) has a phase insensitive frequency comparator (18) including an up/down counter (26) incremented one way by loop frequency pulses (on 28) and incremented the other way by reference frequency pulses (on 30) and which yields error correction signals (on 22 and 24) to adjust loop frequency when the counter overflows or underflows given limits. Timing means (32) is provided at the input (28, 30) to the counter (26) and prevents any clock pulse from being lost by ensuring a sufficient time gap between pulses. A sample and hold phase detector circuit (16) is provided at the data acquisition input to the loop (10) and enables successful acquisition and lock-on even with many zeros between the incoming data bits, and does so with a minimum number of components.

Abstract: A servo mechanism is illustrated which uses pulse pairs for positioning a motor by a given increment with a velocity sensing sample and hold feedback utilized to minimize detrimental repositioning forces. The velocity sensing is accomplished after the end of the drive pulses since this sensed voltage is proportional to the magnitude of the detrimental repositioning forces.

Abstract: Stability of connectors on printed circuit boards is achieved by using connectors having three legs for mounting the connector to the printed circuit board. Each leg has a shoulder stop that provides spacing above the circuit board.

Abstract: A feedback network for a linear amplifier provides for sampling the input signal and removing the modulation from the input signal while maintaining a 180.degree. phase relationship with the input which is essentially the process of converting it into a square wave. The output signal is also sampled and the envelope separated from the sampled output signal and used to drive a modulator which modulates the square wave. This modulated square wave is then mixed with the input signal prior to amplification. In addition, automatic gain control is provided by a level comparator that compares the output signal with the input signal and the results of the comparison is used to attenuate or to control the level of the modulated square wave.

Abstract: A microwave frequency converter is provided by a single mixer of the diode-quad bridge type which circulates generated image frequency within the bridge. The bridge is connected between balun coupled RF microstrip conductors and unbalanced LO microstrip conductors. There is zero connection length between the diode pairs to reduce conversion loss by preventing a phase shift between the image frequencies. Mutual isolation is provided between the RF, LO and IF signals over a broad frequency range. In an alternate utilization, the converter accepts transposed RF and LO signals, for broader bandwidth operation. The circuit may also be implemented as an up converter.

Abstract: A muldem (100) has a monitor (101) for testing data path failures through the muldem (100) by comparing the latter's input and output. The monitor (101) includes comparing means (806, FIGS. 13a and b) with a data comparator (880, FIGS. 13b and 17) for bit error detection by comparision of a pair of data streams (A+B) processed through the monitor (101) from the input and output of the muldem (100). The data comparator (880) delays one of the data streams (A) by a fixed amount and variably delays the other data stream (B), and then slipshifts the data streams in time until they are in alignment to be compared. The data comparator (880) detects noncoincidences of bits in the two data streams and counts such errors over a given sampling interval, providing a bit error rate. If this rate is above a user selectable threshold, then a malfunction in the tested data path is probable, so the path is retested, using a longer sampling interval, to improve the statistical accuracy of the test.

Abstract: An error detection circuit detects prolonged sequences of unchanged logic state in a data busing structure. The circuit generates a complementary two rail logic output from a pair of flip-flops. The circuit includes a comparator which compares the logic state of the data input from the bus with the output of one of the flip-flops, and which inputs alternate opposite logic states to that flip-flop as long as the data input exists for a time in the same logic state as the output of the one flip-flop during a cycle. The complementary two rail output changes every cycle to actively exercise the error detection circuit and prevent silent failures therein. The circuit is self-checking because internal failures yield non-complementary outputs.

Abstract: A muldem (100) has a monitor (101) for testing data path failures and standby data protective switching means (108, 109) providing alternate standby data paths in the event of a malfunction. The system accepts a maximum of fifty-six standard low speed T1 lines (1.544 Mb/s), fourteen standard intermediate speedT2 lines (6.312 Mb/s), or any combination of T1 and T2 lines to generate two standard high speed T3 lines (44.736 Mb/s). The structure allows for partial equipping of low and intermediate speed circuits by accepting any number of circuits up to the maximum capacity of the high speed circuits. The system provides automated adjustment for expansion and contraction of the system while in operation. Individual T1 and T2 signal paths may be added or removed with no disturbance to any other path. The monitor automatically adjusts to test data paths through added T1 or T2 circuits and to ignore data paths through removed T1 or T2 circuits.

Abstract: Electrical consumption registered in a watthour meter is converted into an electrical analog suitable for transmission to a remote monitoring site by reflecting light off the watthour meter rotor, the light being periodically interrupted during each rotor rotation by a darkened light absorbing area of the rotor which traverses the light beam, passing the light to and from the meter through fiber optic cables and digitally counting at a distant location each of the pulses corresponding to the rotor rotation which are transduced from the light reflections. By generating the light from an AC signal, AC signal processing techniques employed in the light reflection detection circuitry ensure a useable electrical analog with minimal likelihood of error otherwise arising from spurious noise and varying ambient temperature related signals.

Abstract: Magnetic field detection apparatus including means for supplying a periodic excitation signal to a rod of magnetic material having high permeability (whether or not it has hysteresis due to retentivity of the core or eddy currents) and means for sensing the external field wherein the material is situated. When the material has retentive properties and there is an external field being detected the flux lag (or lead) relative to the periodic excitation is longer for one flux direction that the other. The difference in these lags provides an indication of the field to be detected. When the material does not have retentive properties, an external field can still be detected by logic circuitry in an embodiment similar to the last mentioned embodiment.

Abstract: A phase-locked loop apparatus for deriving clock pulses from return-to-zero data pulses is disclosed. It includes a phase detector for computing the difference, in time, between that portion of a detected data pulse which occurs before a clock pulse edge and the portion after the clock pulse edge. The difference, once computed, is held for a long period thereafter and is used to drive a voltage controlled oscillator. The voltage controlled oscillator generates the clock pulses which are applied to the phase detector and which comprise the output of the apparatus.

Abstract: A sliding power supply for a radio frequency power amplifier provides power to the power amplifier that is indirectly controlled by the load impedance voltage standing wave ratio of the amplifier. The overall results being an enhancement or improvement in the efficiency of the RF power amplifier into a varying RF load mismatch.

Abstract: An integrator is illustrated which provides normal action integration operation as long as the input signals remain a given polarity. However, when the input signal changes in polarity, the integrating capacitor is substantially instantly discharged and then the integrator integrates, from the discharged capacitor condition, in the changed polarity direction until the input signal polarity again changes.

Abstract: A rate converting bit stream demultiplexer and related multiplexer are disclosed. In the demultiplexer, there are two groups of N cascaded shift registers. A serial input data stream is alternately entered first into one of the groups of registers and then into the other. While the input data is being entered into one of the register groups, it is being simultaneously read from each shift register of the other group at a rate equal to the bit rate of the input data stream divided by N. In the multiplexer, the situation is reversed, with data being read from multiple input channels into each shift register in one group, while data is being read from a single output of the cascaded registers of the other group at a rate equal to N times the bit rate on the input channels.

Abstract: A modulation device that has a means for minimizing the time required for the diodes to alternate conductive and nonconductive states. The modulation device as disclosed includes an input port for the signal that is to be mixed, a local oscillator port for the application of the switching signal and a sum port for providing the product of the two signals. Modulation is achieved by the operation of the diodes that are used as switches which are controlled by the local oscillator signal.

Abstract: An antenna coupler samples the power transferred between the transmitter and the load, and at two equal distance points from the load. The coupler, based upon the value of the samples, connects a tuning stub to the transmission lines that ensures matched impedance conditions between the transmitter and the load.

Abstract: A polarization key is disclosed for installation in an electrical connector on a backplane circuit board. The key has a tongue portion for insertion into the connector, engaging the resiliently biased contacts of the connector. A tab portion of the key projects outwardly from the connector to prevent the insertion of another circuit board therein unless the other circuit board is properly slotted to mate with the key. A pair of legs extend from the tab portion of the key along the outside of the connector to enter holes provided in the backplane circuit board.

Abstract: Circuitry is disclosed for detecting signal amplitudes of a signal which is phase indicative of a digital logic level and providing a feedback signal for use in amplitude adjusting the signal to have a substantially zero slope over the relevant frequency bandwidth and zero notch in the middle of the band. The compensation is obtained by applying a voltage to variable impedance pin diodes which form part of a reactive load circuit.