Service manual

5-26 Samsung Electronics
5-1-7 FAX TRANSCEIVER
5-1-7-1. GENERAL
This circuit processes transmission signals of modem and between LIU and modem.
This circuit is added only to SMARTJET.
5-1-7-2. MODEM (U21)
KS16116 is a single chip fax modem. It has functions of DTMF detection and DTMF signal production as well
as functions of modem. TX OUT is transmission output port and RX IN is received data input port. /POR
signal controlled by MFP controller (U15:KS32C6200) can initialize modem(/RST_OUT) without turning off
the system.
D0 - D7 are 8-bit data buses. RS0 - RS4 signals to select the register in modem decide the mode. /CS is a sig-
nal to select modem chips. /RD and /WR signals control READ and WRITE respectively. /IRQ is a signal for
modem interrupt.
Transmission speed of KS16116 is up to 9600bps.
5-1-7-3. TRANSMITTER
This circuit processes transmission output, analog signal of modem(KS16116).
Output signal in each mode goes out of modem (TXOUT:U21-44). After D/A signals are smoothed and fil-
tered through active filter (U5-6,7:R270,R277,C130), they are buffered under OP AMP(U5-2, 1:R291, C139,
R298, C150) and put out to LINE through LIU board.
5-1-7-4. RECEIVER
In the receiving mode, analog signals coming in through LIU board are amplified at OP AMP(U6-2, R293,
C141), and then transmitted to input terminal of modem (RXIN:U21-45) through smoothing filter (U6-6,
7:R273, R274, C126).
Fig.5-1-18. FAX TRANSCEIVER
FAX TRANSMISSION
FAX RECEPTION
MODEM
KS16116
(U21)
LIU