IDU consists of MUX/DEMUX, Satellite modem (modulator-demodulator), EDU (Encryption decryption Unit) and subscriber interfacing part.
• MUX/DEMUX:
It is used to provide multiplexing of voice channels and data channels at the transmit end while demultiplexing at the receive end.
• Satellite Modem:
It consists of modulator at transmit end and demodulator at receive end. Modulator does modulation of baseband information (voice/data) at IF (either 70+/-18 MHz or 140+/-18 MHz). Modulator generated modulated IF frequency. Demodulator does the reverse operation i.e. demodulation of modulated IF to retrieve baseband information.
• Baseband interface:
This is voice and data connectivity. Usually voice can be a subscriber line or exchange connection with 2W E&M or 4W E&M etc. configurations.