Apparatus for interfacing analog telephone in ISDN terminal adapter

An apparatus for interfacing an analog telephone in an ISDN terminal adapter provided with a coprocessor for controlling and processing of the communication with network termination equipment, said apparatus comprising:

• a combocodec which converts digital audio signals generated from said co-processor into analog audio signals to supply the converted analog audio signals to the telephone, and which converts analog audio signals from the telephone into digital audio signals to supply the digitized audio signals to a coprocessor;
• a ring generator which generates a ring signal in response to a ring generating control signal transmitted by the co-processor;
• a DC-voltage converter which receives power from a computer power supply, and performs a DC-voltage conversion to supply a voltage required for a TIP/RING loop operation;
• a subscriber line interfacing circuit connected to said DC-voltage converter, said combocodec, and the telephone, which supplies a telephone driving voltage generated from said DC-voltage converter to the telephone, transmits a bilateral audio signal between the telephone and said combocodec, and which monitors current or voltage on the TIP/RING loop to distinguish the hook status of the telephone, said subscriber line interfacing circuit including ring and tip terminals, a ring feed terminal, a control signal input terminal and a ring driving terminal;
• means for supplying a ring supply control signal to said subscriber line interfacing circuit, said subscriber lines interfacing circuit generating a ring driving signal responsive to the ring supply control signal;
• a relay connected to the ring driving terminal of said subscriber line interfacing circuit, said ring generator, and the ring feed of said subscriber line interfacing circuit, which transmits the ring signal generated from said ring generator to said subscriber line interfacing circuit responsive to the ring driving signal;
• and
• a tone decoder which decodes a dual tone multi-frequency signal from among said audio signals transmitted from said subscriber line interfacing circuit to said combocodec, which transmits said decoded signal to said co-processor and
• whereby call set-up is performed independent of simultaneous operation of a computer.