Abstract: A method and apparatus are provided for determining the quality of a speech transmission, including temporal clipping, delay and jitter, using a carefully constructed test signal (300) and digital signal processing techniques. The test signal that is to be transmitted through a speech transmission system (100) is created (700). Then the test signal is transmitted through the speech transmission system such that the speech transmission system creates an output signal that corresponds to the input signal, as modified by the speech transmission system (702). The test signal includes multiple segments (500) of speech signals interleaved with periods of silence. The periods of silence vary in duration according to a predefined pattern. Each segment of speech signals includes multiple predefined speech samples or symbols (400, 402, 404, 406, 408, 410, 412, 414) interleaved with a plurality of silence gaps. The speech samples have a common period of duration, but the silence gaps do not.

Abstract: An enhanced Time Slot Interchange (TSI) facility, in addition to serving synchronous channels of communication, decomposes and composes asynchronous data cells to provide real-time communication among and between both synchronous and asynchronous channels served by a network access switch. An asynchronous cell comprises a 5 byte header and a 48 byte payload. The payload comprises voice samples from a temporarily defined set of DSO facilities and/or data from a variety of data facilities. Time slots of the TSI are temporarily assigned to the payload bytes of each incoming asynchronous cell; the payload bytes are stored in memory locations corresponding to those time slots; and the stored data is read out during time slots assigned to the destination channels of communication. The TSI comprises three data rams to accommodate for frame to frame jitter in the time of arrival of payload samples.

Abstract: A subscriber loop carrier system using digital multiplex techniques is disclosed in which remote subscriber loops include multiparty lines. Four party fully selective ringing signals are detected at the central office terminal of the system and converted to cyclic codes which are detected at the remote terminal with simple asynchronous circuits. The code generation and detection circuits are implemented with multiple output inverter circuits which provide simple logic structures for integrated circuit realization. Standard polarized ringing signals are applied to either conductor at the remote terminal of the system to ring the proper party.