Abstract: A digital conferencing arrangement for use in a digital telecommunications switching system. Digital coded signals representative of sampled analog signals are compared and the results of the comparison noted to identify the present speaker in the conference. A comparison result indicating a proposed new speaker initiates a delay interval during which subsequent samples are compared to assure that the proposed new speaker indeed has the largest analog signal during the delay window. Upon verification of the proposed new speaker, the control of the conference circuit is transferred to him.

Abstract: An apparatus and method for testing for faults in an analog-to-digital (A/D) section and a digital-to-analog (D/A) section of a code converter in a digital time division, multiplex telecommunications system are disclosed. The A/D section is tested by connecting a digital test pattern via the switching network to the D/A section and monitoring for faults by comparing the resulting output to a reference value. The A/D section is tested by interconnecting the A/D section to be tested between a first previously tested D/A section and a second previously tested D/A section and then connecting the digital test pattern to the first D/A section while monitoring the output of the second D/A section for faults.

Abstract: A voice-frequency RC-active filter comprising a plurality of resistors and generalized impedance converter networks for synthesizing the frequency response of a preselected LC filter. Each generalized impedance converter network includes a pair of operational amplifiers and a plurality of impedances Z1, Z2, Z3, Z4 and Z5 interconnected with the amplifiers to provide the network with a driving point impedance ##EQU1## in which at least one of the impedances in both the numerator and the denominator of Zi includes a film-type resistor. At least one of the film-type resistors included in the impedances Z1, Z2, Z3, Z4 and Z5 is functionally trimmed to tune the filter. The capacitors in the filter are preferably discrete polycarbonate capacitors with a capacitance tolerance of .+-.5%, and all having the same value.

Abstract: A telephone system usable for example in hotels or the like and in which each of a plurality of telephone sets is equipped with a special status indicator or signal light as well as the usual bell, the system being characterized in that the indicator is automatically excited without ringing the bell by voltages applied from the ring generator whose output signal is connected across the tip and ring leads of a telephone line when the latter is placed in a special status (message waiting) by a status signal in the control unit. The ring generator is constructed to produce special status indicator excitation voltages during the "bell silent" intervals of its output signal, and the indicator is periodically actuated by connecting that output signal across the tip and ring leads of telephone sets, which are in the special status, during at least a portion of such intervals.

Abstract: An electronic hybrid for coupling signals between two wire and four wire transmission circuits, and capable of meeting the operating requirements of practical telephone systems. The hybrid includes a pair of terminating impedances serially connected between the two wire port and the circuitry driving that port, the impedances being precisely matched and coupled to a.c. ground, thereby providing a hybrid with excellent longitudinal balance. Amplifiers driving the two wire port through the terminating impedance may be biased to couple a d.c. potential to the two wire line whereby the terminating impedances serve as battery feed resistors. Reverse signal recovery is provided by an amplifier differentially connected to the two wire port, achieving excellent longitudinal rejection and further allowing the amplifier to serve a supervisory function. Two of such hybrids, connected back to back, with amplification interposed therebetween, form an improved transformerless repeater.