Abstract: The invention is applicable to delta modulation. A method of codifying the bit-stream for more efficient storage and transmission is disclosed. The number of pulses from the a-to-d converter is counted, per batch of B clock beats. The count, or tally value T of the batch, may be issued as an N-bit group, e.g. a 4-bit nibble. The order and spacing of the pulses within the batch is ignored. When the signal is rebuilt, a batch of B clock beats are counted out, T of which are pulses. One value which the nibble can take is reserved and used to indicate a period of silence, by replacing a whole frame of silent nibbles. Both a fixed frame length and a variable frame length are disclosed. For greater sensitivity, the extreme tally values may be utilized to signal a change in the gain or response of the system. A median tally value may be used to cancel the gain change.

Abstract: A fault detecting system is provided for detecting fault of an ADPCM codec for transcoding an input signal between an ADPCM and a PCM to produce a first code converted signal. The ADPCM codec has a data RAM for storing data used for the transcoding and is provided with a data transmitter for transmitting the data. A fault detecting processor receives the data and generates a second code conversion signal from the received data. The fault detecting processor compares the first and the second code converted signals and produces a fault signal when both of the signals are not coincident with each other. The input signal can be supplied to the fault detecting processor directly or as a part of the data transmitted thereto. The fault detecting processor can detect fault of a plurality of ADPCM codecs by a time division fashion.

Abstract: A binary tree search system locates and outputs video data stored in a ROM, the data corresponding to received variable length uniquely encoded codewords. The data for each codeword is stored at a unique ROM address, each address corresponding to a tree leaf. Certain ROM locations not associated with complete codewords include a partial search address for the next search node, the remainder of the search address for each node comprising a bit of the serial received encoded data. When the received bits complete a codeword, the last received bit and the prior accessed ROM stored partial address form a pointer address to a tree leaf that accesses that ROM location containing the data corresponding to that codeword. Flags are generated by each accessed location to indicate whether or not a codeword has been found. If a codeword is found, the search is restarted at the tree root.

Abstract: A data interface circuit for use when interfacing between two communication links communicating frames of digital data in PCM and ADPCM formats is provided. The data interface circuit provides control information for selecting one of a plurality of algorithms to control the transformation of data between a plurality of PCM and ADPCM formats. A single encoded control signal is utilized to establish frame boundaries and to select a predetermined one of the plurality of algorithms to use in converting between PCM and ADPCM data.