Abstract: In a pipelined processor, when a conditional branch is effected in accordance with a state of calculation generated by immediately previous instruction, it is necessary for a conventional technique to insert a NOP (no operation) instruction before a conditional branch instruction. This lowers the processing efficiency. In order to solve this problem, a delay circuit generates a clock signal .phi.' which is supplied to a program counter and an instruction memory. The clock signal .phi.' is delayed behind a system clock .phi.. This obviates the need to insert such a NOP instruction and the processing efficiency is improved.

Abstract: A speech communication apparatus of the present invention includes, in addition to an echo canceller for canceling an acoustic echo generated in a hands-free speech space, a chirp signal generating unit and a training unit. The chirp signal generating unit generates a chirp signal adequate for initial training of the echo canceller. The training control unit enables the chirp signal generating unit to generate a chirp signal, when a predetermined condition for starting hands-free speaking is satisfied, and a chirp tone corresponding to the chirp signal to be output as a volume-amplified tone from the hands-free speaker. The echo canceller performs initial training of the echo canceller based on the chirp tone.

Abstract: This invention provides a novel speech coding system which recursively executes a filter-applied "Toeplitz characteristic" by causing a drive signal (i.e., an excitation signal) to be converted into a "Toeplitz matrix" when detecting a pitch period in which distortion of the input vector and the vector subsequent to the application of filter-applied computation to the drive signal vector in the pitch forecast called either "closed loop" or "compatible code book" is minimized. The vector quantization method substantially making up the speech coding system of the invention is characteristically used by the system.