Abstract: An Integrated Services Digital Network module includes a time division multiplexed switching network. Subscribers are connected to the time division multiplex network via a number of facility interface cards. These facility interface cards provide for two wire subscriber connection, four wire subscriber connection, T1 line connection and for three port conferencing arrangements. Originating and terminating multiplexers connect the facility interface cards to the time switching network. Another subsystem provides protocol interfaces for HDLC channels. Another subsystem provides interface to central office switching systems. Lastly, a general purpose computer and file computer system provide for the storage of database and form maintenance functions. Each subsystem is controlled via processor which is linked with each of the other processors by an ethernet local area network. This system provides both Primary Rate (23B+D) and Basic Rate (2B+D) interfaces to the subscribers.

Abstract: A method for generating PCM logarithmic values from linear values and storing these values in memory for efficient and rapid data retrieval is shown. This is an off-line method of generating the contents of a programmable read only memory for rapid on-line conversions from linear to logarithmic PCM values by an ISDN system. This method generates either negative or positive PCM values. An initial value and memory address are determined. Next, memory address is incremented and is PCM value decremented. The resulting PCM value is stored at successive locations throughout the memory. Each PCM value comprises a step of a segment. These operations are iterated for each of the segments required for conversion for both positive and negative PCM values.

Abstract: A time shared multiport conference arrangement includes an additive PCM speaker circuit. The additive PCM speaker circuit eliminates the need for loudest speaker detection and the last speaker memory of conventional conferencing arrangements. The additive PCM speaker circuitry operates in an on-line, real time environment to allow rapid conversion and summing of speakers' PCM voice samples. Since the PCM voice samples are logarithmic in nature, they are not directly combinable. The additive PCM speaker circuitry provides for converting the logarithmic PCM signals to linear form. Next, the linear signals of up to three conferees are buffered. Then the speakers' linear form samples are added and each combination reconverted from linear to logarithmic form. The additive PCM speaker circuit simplifies the complex processing logic usually associated with loudest speaker detection systems and thereby improves the real time operation of the conferencing arrangement.