Table of Contents
Advertisement
3-4.
NCU Board
(1)
Overview
• The NCU board has various functions such as line connection, ringer detection, off-hook
detection, polarity detection, and dialing pulse transmission.
Block diagram
CN5
(2)
Function of each block
• LINE is a modular port for connecting a phone line.
• TEL is another modular port to connect an extra telephone set.
• The dialing pulse transmitter outputs dial pulses controlled by the MFB2 board.
• The ringer detector provides an automatic reception function. It isolates a receiver ringer
signal with a photo-coupler, and outputs it to the MFB2 board. The ringer signal is
counted by the counter of G/A.
• The polarity detector uses two photo-couplers to detect the DC polarity of the line. If
either of the detected signals is "1", the other signal is "0".
• The off-hook detector shares a circuit with the polarity detector, and detects off-hook, i.e.,
direct current.
Circuit
M-11
SW
Circuit
CN11
TEL
CN12
LINE
Advertisement
Table of Contents
