602E52970
2-13
2.3.3 Block Diagram of the Network Control Unit Board
The NCU (Network Control Unit) board acts as the physical interface with the
telephone line. The NCU board is available in several versions, to suit the specific needs
of each country.
The NCU board also contains the integrated phone circuitry.
Fig. 2-11 Block diagram of a generic NCU board
Amplifier
Selector
relay
Line
transf.
Call
detector
Current
detector
TX
RX
Handset
TAD
Selector and
modem-line
connection relay
Motherboard
Telephone line
Telephone-line
connection relay
Receiver
detector
relay
Telephone
circuit
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