Digital audio signal transmitting apparatus

A digital audio signal transmitting apparatus comprising:

• a) an audio signal decoding device which includes:
• a1) a decoder for decoding a digital audio signal of a given code into an original digital audio signal;
• a2) a pseudo PCM signal generator for interposing the digital audio signal of the given code in a predetermined background PCM signal;
• a3) a first operation 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 an operation mode change signal;
• a4) a bit pattern adder for interposing a bit pattern signal in a signal selected by the first operation mode change switch, the bit pattern signal including bits in a predetermined pattern;
• and
• b) an audio signal compressing and encoding device which includes;
• b1) an encoder for compressing and encoding an incoming digital audio signal into another digital audio signal of the given code;
• b2) a signal extractor for extracting a digital audio signal of the given code from the incoming digital audio signal;
• b3) a bit pattern detector for detecting whether or not the incoming digital audio signal contains the bit pattern signal, and for generating a signal in response to a result of said detecting;
• b4) a logic operation circuit for executing a given logic operation from the output signal of the bit pattern detector, a sending signal, and a receiving signal, the sending signal and the receiving signal represent whether or not communication is being currently executed, and for generating the operation mode change signal in response to the output signal of the bit pattern detector, the sending signal, and the receiving signal;
• b5) a second operation mode change switch for selecting one of an output signal of the encoder and an output signal of the signal extractor in response to the operation mode change signal.

An apparatus connected to a transit switch and operating on an incoming digital audio signal sequentially representing dial information and audio information, comprising:

• a decoder;
• first means for continuously feeding an incoming digital audio signal to the decoder and transmitting an output signal of the decoder to the transit switch until the whole of the dial information represented by the output signal of the decoder is received by the transit switch;
• and
• second means for enabling the incoming digital audio signal to bypass the decoder and travel directly to the transit switch after the dial information is received by the transmit switch.