Abstract: A counter slip control circuit is described for digital transmission systems wherein the counter uses a feedback circuit to define the permissible counter states. The slip control input modifies the feedback function so that certain counter states are either repeated or skipped. A repeated counter state is equivalent to retardation of the counter output signal phase. A skipped counter state is equivalent to advancing the counter output signal phase. The slip control gate is eliminated from the clock input line to the counter and instead is included in the feedback path which eliminates the skew problem and permits the equivalent of adding clock pulses without the requirement for logic speeds of twice the normal clock speed.

Abstract: A magnetically operated switch especially useful in telephone applications includes a transformer having a plurality of windings on an E-frame core and a reed switch magnetically coupled to the core by a plurality of high permeability strips which are placed in juxtaposition with the core and which have rolled end portions for supportably receiving the reed switch. The switch may be used in a hybrid junction for dial pulse detection.

Abstract: A weighted resistance network under control of combinational and sequential logic circuits provides a separate reference voltage at each of the digit times of the pulse code for comparison with an amplitude sample at the coder input. The difference voltage is used to derive the pulse code which is compressed in a piece-wise manner because of the use of a weighted resistance network. A decoder operates in a similar manner to produce a quantized output from a weighted network under control of a logic circuit responsive to the incoming uniform pulse code.

Abstract: A test system for a T carrier type telephone PCM communications system converts typical trio type pulse sets to quadruple sets in order to eliminate the dc offset. Thus, the test signal can be passed through several successive spans or through marginal repeaters in a manner similar to an ordinary data signal. The trio to quadruple conversion is accomplished by a stuffing procedure which compensates for any ambiguity in the audio crossover when the initial test signal is being produced. A reconverter may be remotely actuated to test any particular span or to loopback the test signal whereby testing may be carried on at a single location for both incoming and outgoing lines.