Abstract: An improved conference technique whereby a number of channels in a telephone switching system employing pulse code modulation for transmission purposes are combined so that a number of subscribers may participate in a common telephone conversation. The conference circuit is provided with a continuous threshold to pass the primary signal and to exclude the reflection. It is only used in the selection process, and for conditions which do not provide the threshold being met, the previous speaker is retained.

Abstract: A restraining apparatus used to secure cable reels during transportation or storage wherein a restraining device is inserted between a flange of a cable reel and a supporting surface and an associated clamp is pivoted and tightened onto the flange securing the apparatus in position.

Abstract: A circuit for obtaining clock timing information from an equalized pseudo-ternary signal, such as is exemplified by a signal using the modified duobinary code, includes a level selector in which the signal is sliced at a predetermined amplitude. A slicing level reference circuit provides the threshold voltage for the level selector so that only the upper level portion of the original is obtained for processing. This upper level portion is applied to an amplifier and then to a frequency selection circuit which is tuned to the clock frequency of the original signal.

Abstract: A calibrated unipolar signal is used to deviate a frequency modulator by a predetermined amount .DELTA.f from a carrier f.sub.2. An automatic frequency control circuit operates to bring the carrier back on frequency and a meter connected in the control circuit will read this departure from normal. During the test for correct deviation, a frequency shifter compensates for the predetermined frequency deviation and the meter would so indicate, e.g., would not change reading from that of carrier alone, if the deviation caused by the calibrated unipolar signal is equal to that incorporated in the frequency shifter. If the reading does change, the modulation sensitivity of the frequency modulator is adjusted until the readings before test (using carrier only) are the same as those under test.

Abstract: The phase detector of this phase lock loop includes a transistor switch shaping the output of an Exclusive-OR gate which combines a data signal with a square wave local clock signal from a VCO for producing a digital error signal that is integrated to produce an error voltage that is applied to one side of a differential amplifier in an active lowpass filter. Other means integrates the local clock signal to produce a reference voltage that is applied to the other side of the amplifier, the output of the latter being a control voltage which drives the VCO. In a preferred embodiment, the reference voltage means and the path between the gate and the one side of the amplifier both include a switching transistor (the two being on a common substrate) and resistors of the same type and value for causing variations in the two input lines to the amplifier to track as a function of time and temperature.

Abstract: Single errors can be detected and corrected in a signal employing a 3-level modified duobinary code. Error correction is predicated on the concept of maximum likelihood of error for the bit having the maximum departure from normal amplitude (error differential). A converter accepts the modified duobinary signal, decodes the signal to obtain a binary output signal and determines the error differential for each bit. Bits of the binary output signals are temporarily stored in a sequential storage device. The error differential is applied to an input of an error analyzer. An error detector determines if an error has occurred during an error correction interval which interval is established by successive extreme levels of the modified duobinary signal. The error analyzer tracks the location of the bit having the largest error differential during each error correction interval.

Abstract: The cooperating contacts of a reed switch each comprise a layer of palladium. A protective layer of ruthenium deposited on the palladium layer prevents the formation of frictional polymers.

Abstract: A buffer amplifier, which prevents loading of the input signal, accepts at its input an amplified and equalized pseudo-ternary signal. The output of the buffer amplifier is a-c coupled to the input of a precision differential amplifier, from which two output signals are obtained. One said output signal is representative of the positive pulses and the other said output signal is representative of the negative pulses of the pseudo-ternary signal. These two output signals are both applied to the inputs of a peak detector and a slicer. The d-c output of the peak detector is also applied as one input to the slicer. Separate outputs are obtained from the slicer, one each for the positive and negative pulse inputs, and these two outputs are summed, and the summed output is then amplified to provide a clock driver output.

Abstract: This chassis has side, top, bottom and rear plates which are made out of sheet stock and where are oriented at 90.degree. with respect to each other. Bifurcated tongues are formed in edges of plates. Elongated slots are also formed in plates at points spaced away from the edges thereof. The slots and tongues are dimensioned and oriented on the plates such that in an assembled shelf, the bifurcated tongues are located in associated slots so as to form square openings defined by walls of the associated slots and bifurcations-openings. Self-tapping screws threaded into the square openings and axially aligned bifurcations-openings cut threads in the walls defining these aligned openings over the full grip length of the screws to hold the plates together.

Abstract: Modified duobinary regenerative repeaters are tested in situ by means of a pulse pattern generator connected to the repeatered span line, a plurality of audio filters, one at each repeater site, a return transmission path and a measuring device for determining the character of the signal output from a selected repeater.

Abstract: The correlation properties of a 7-level correlative waveform permit detection of errors due to irregularities and impairments in the transmission facility, where these errors violate the correlation patterns of the waveform. The received 7-level correlative waveform is first decoded to obtain a pair of binary outputs which are representative of the original binary signal at the transmitter, except for errors that might have occurred during the transmission period. The pair of binary signals are operated on to obtain coded binary signals and their delayed counterparts. These coded binary signals are used to establish the effect of presence or absence of a top or bottom level that would result from the formation of a nonbinary correlative signal. If an error has occurred during transmission, the extreme levels of the locally generated signal will not normally coincide with those of the received signal.

Abstract: A circuit card connector and support device, for supporting and providing electrical connections to two or more printed circuit cards of less than full size within a printed circuit card cage or rack at any position normally occupied by a full sized card. The connector, includes mounting members disposed to mount within a card cage or rack and an arrangement for slidably receiving and electrically connecting to at least one circuit card. The support device, is disposed to receive a second edge of at least one circuit card and includes latching guide members adapted to interlockingly engage the connector and position the support device perpendicular to the front surface of the connector. An indexing projection, on the support device engages the connector locking the support device in position.

Abstract: A dual coil bobbin assembly adapted for use in the manufacture of coil elements for telephone receivers comprising two spool like sections joined by a flexible hinge and adapted to have the bobbins of each coil positioned axi-symmetrically on a temporary basis whereby both coils maybe mechanically wound on the bobbin assemblies. After winding is completed the coils may be repositioned with each bobbin parallel and in appropriate position for mounting in a telephone receiver assembly.

Abstract: The embedding network of a microwave oscillator comprises three lengths of parallel conductors supported above a ground plane and having odd and even mode short circuits thereon. Two of the conductors are connected to different ones of the electrodes of a bipolar microwave transistor which has a third electrode connected to ground. A load is connected between the third conductor and ground. Physical and electrical characteristics of the network are varied to cause parameters thereof to be desired values which yield maximum output power and oscillation at desired frequencies.

Abstract: A circuit for simulating environmental dependent phase shifts in a pulse train includes circuitry for generating a reference pulse train and two cascade connected phase modulators for producing a phase shifted pulse train wherein the phase relationship between corresponding pulses of the phase shifted pulse train and the reference pulse train varies in accordance with a predetermined variable phase shift. Circuitry is further included for selectively applying the phase shifted pulse train to utilization equipment when pulses of the phase shifted pulse trains have a first predetermined phase relationship to pulses of the reference pulse train and for selectively applying pulses of the reference pulse train to the utilization equipment when pulses of the phase shifted pulse train have a second predetermined phase relationship to pulses of the reference train.Cumulative phase shifts of greater than 360.degree. may be obtained.

Abstract: A substrate carrying electrical circuit patterns and elements is supported in an upright position on a printed circuit board by a clip so as to restrict rotational movement of the substrate from that position when pins and plated through holes on the substrate and board are engaged. The clip comprises a body having a flat bottom for contacting one side of the board and a first-cylindrical peg depending from the bottom. Spaced-apart sections on one side of the body are in a common plane perpendicular to the bottom with a protrusion near the top of the body extending beyond this plane. A second-rectangular peg also extends from the one side of the body past the common plane, with the base of the second peg being in line with the flat bottom. A trough in the protrusion receives one edge of the substrate, with one side of the latter contacting the side sections in the common plane, and the opposing edge of the substrate being proximate the bottom of the body.

Abstract: Apparatus and method for generating a multilevel correlative signal wherein the multiple levels are digitally generated. A serial binary bit stream is first converted into two parallel binary bit streams each at half the bit rate of the original serial binary bit stream. The parallel bit streams are encoded in accordance with the relation B = C - .DELTA..sup.2 C MOD 4; where B is the original waveform, C is the resultant waveform, and .DELTA..sup.2 indicates two units delay or 2T seconds where 1/T is the parallel speed in digits per second. Next the binary encoded bit streams are digitally converted to a 7-level waveform; and, finally the 7-level waveform is transformed into an analog signal which retains the 7-levels and provides a band limited 7-level signal related on a one-to-one basis to the binary input signal.

Abstract: A modified duobinary signal is separated into two (odd and even) pulse trains, each of which is representative of a bipolar pulse train. Each representative bipolar pulse train has a bit rate one-half that of the modified duobinary signal. Violations of the modified duobinary coding rules appear as violation of the bipolar coding rules. The bipolar violations which occur are detected separately for the odd and even pulse trains. The detected errors are read into an error combiner and are read out serially at the original modified duobinary bit rate.

Abstract: A low insertion force electrical connector assembly for connecting to a printed circuit board, having a plurality of spaced contacts carried by and adjacent one edge. The body member has a circuit board receiving channel extending longitudinally along the body member for receiving the edge of the printed circuit board having the spaced contacts. The channel includes a pair of opposing fulcrums intermediate the bottom and the opening edge, one on each interior wall of the channel. The fulcrums leave a space therebetween for the passage of the circuit board. A first series of conductive strips is positioned along a first interior wall of the connector channel between said fulcrum and the bottom of the channel, and a second series of conductive strips is positioned along a second interior wall of said connector channel between the fulcrum and the opening edge of the channel.

Abstract: A method for the electrodeposition of a relatively thick (20 to 45 microinches) layer of ruthenium includes the step of pulse current plating an intermediate layer of gold over the substrate to be plated. The ruthenium layer so obtained is characterized by low internal stress and an absence of surface cracks.