Abstract: An identification number inserting portion 26 in a multiplexing portion 33 in an audio transmission system 10 inserts a connection identification number for own connection into an audio band signal cell which is to be transmitted via an up line 60. An identification number detecting portion 30B detects that the connection identification number is transmitted again from a switching system 1 to the audio transmission system 10 via a down line 70.

Abstract: An echo canceler for suppressing an echo of a receive signal contained in a transmit signal directed to a telephone circuit and transferring the transmit signal subjected to echo suppression to the telephone circuit. The echo canceler includes a pseudo echo path for attenuating and delaying the receive signal supplied from the telephone circuit and adding the delayed receive signal to the transmit signal, and an echo cancel circuit for estimating a transfer function of the pseudo echo path on the basis of the receive signal supplied from the telephone circuit and the echo of the receive signal, generating a pseudo echo on the basis of a value of the estimation and the receive signal, subtracting the pseudo echo from the transmit signal passed through the pseudo echo path, and thereby transferring the transmit signal subjected to echo suppression to the telephone circuit.

Abstract: A voice band signal is compression-encoded at a voice compression-encoding portion and is assembled into a cell at a cell assembling portion. Conversely, the voice band signal is disassembled at a cell disassembling portion and is decoded at a voice compression-decoding portion. When, from both of up and down data judging portions, receiving a judgement of coincidence of the voice band signal with a signal at the time when the line is unused, a timer counts a continuation time. When the continuation time exceeds a protection time, a protection time judging portion causes the cell assembling portion to stop the cell transmission. When, from either of the up and down data judging portions, receiving a judgement of no coincidence with the signal at the time when the line is unused, or when the continuation time does not exceed the protection time, the cell assembling portion is directed to transmit the cell.

Abstract: An audio signal encoding device has a decoder for decoding a digital audio signal of a given code; a pseudo PCM signal generator for interposing the digital audio signal of the given code in a predetermined background signal; a first mode change switch for selecting one of an output signal of the decoder and an output signal of the pseudo PCM signal generator in response to a mode change signal; a pattern change switch for selecting one of a first bit pattern signal and a second bit pattern signal in response to first and second pattern change signals: and a bit pattern interposer for interposing a bit pattern signal selected by the pattern change switch in a signal selected by the first mode change switch.