3-34
CIRCUIT DESCRIPTION
Samsung Electronics
Repair Manual
3-7 LIU PBA
3-7-1. SUMMARY
LIU WIRE CONNECTS Main B’D’s MODEM AND LINE PARTS, AND IMPEDANCE MATCHING (AC, DC), RING DETEC-
TION PART and LINE SEIZURE (DIALER).
3-7-2. DC MATCHING PART
Normal movement range of LIU is 12mA ~ 9mA.
Adapting CTR21 standard, the regulation limits to 60mA CURRENT flow through the terminal.
Therefore, select (*:for EU PIT) Option to connect necessary items then the current through LIU will not exceed 60mA.
• CTR21 Standard(Europe) : 12mA~60mA • OTHER Standard (U.S.) : 12mA~90mA
DC has a character to pass through the LINE. And with Q1 (VN2410) GATE section’s LINE INPUT corrent and Q1 Source
connection to R20, can be decided as follows :
• -VDCR = VL1 + ILINE X R20
(VDCR : Tip-Ring CD Voltage, ILINE : Current flow)VL1:Line Input Voltage, VL1=VBD1+VCE(Q2)+VDS(Q1)
3-7-3. AC MATCHING PART
Basic LIU’s AC IMPEDANCE is 600 and uses R47. 48. C36 to possibly control combined IMPEDANCE.
• U.S. Usage : A terminal IMPEDANCE Æ 600W(±30%)
• CTR21 : A Terminal IMPEDANCE Æ 270+750W//150nF
3-7-4. DIALER PART
*MF DIAL
DTMF Dialing is controlled by MODEM and should be selected by appropriate LEVEL and On-off Time output based on each
countries’ own National specification.
• Tolerance : ±1.5%
High Group : 1209, 1336, 1477, 1633Hz
Low Group : 697, 770, 852, 941 Hz
*DP DIAL
Controls from MAIN through / DP-Terminal.
for U.S.Usage, set time to DF signal of 40:60 M/B. DP signal is made of U6 (pcb817). The DC current which flows thru Q2
Base is regulated by On/Off switch and turns to DP dial signal with a COUPLER.
• CTR 21 does not have telephone capability but has the number 3 and 4 Line Connection. No DP condition but possibility
to get approval only on DTMF Dial based terminal.
U.S. Usage CTR21
High Freq Level -9.0+2.0/-2.5 -7.0 +1.0/-2.0
Low Freq Level -9.0+1.0/-2.0 -11.0+2.5/-2.0
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