Network Control Board (Ncu) - OKIDATA OF1000 Service Manual

2.2.07 Network Control Board (NCU)

The NCU-U board receives the modulated data from the MCNT-150 board and transfers the data
to the line board.
The NCU board performs the following functions during the transmit operation.
· Unit connection / disconnection to the telephone line via the CML Relay
· Dial pulse generation
· The PIS Tone detection
· Off-Hook Detection (Line Current Detector)
· Tx Output Signal Attenuation (normally 9 db 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 OF1000
Chapter 2 Principles of Operation
Page: 33