Network Control Unit (Ncu) - OKIDATA OF2600 Service Manual

1.2.07 Network Control Unit (NCU)

The network control unit receives the modulated data from the main control board and transfers the data
to the line interface board.
The network control unit performs the following functions during the transmit operation.
· Unit connection / disconnection to the telephone line via the CML Relay
· Dial pulse generation
· PIS tone detection
· OFF-HOOK detection (Line Current Detector)
· TX output signal attenuation (normally 9 decibel output)
· Separation of the TX and RX signals (performed by the Hybrid Transformer)
· Impedance matching (the 600 ohm impedance of the telephone line)
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Service Guide OF2200/2400/2600
Chapter 1 Principles of Operation
Page: 29