Samsung SF-530 Service Manual page 116

CIRCUIT DESCRIPTION
3-3-3 Detailed Spec.
TEL_LINE INTERFACE CIRCUIT
1) TEL_LINE INTERFACE CIRCUIT
• It is an interface that physically connects facsimile to the PSTN (public switching telephone network) through TIP and
RING as in fig. 1.
• ARS 1-3 protects the system from voltage overload such as the surge coming through PSTN. ARS 2 and ARS 3 are
used as overload protection in common mode (between TIP/RING and FRAME GROUND). ARS 1 is used as over-
load protection in normal mode (between TIN and RING) and it uses ARRESTOR for 600V. However, arrestor's rated
voltage differs from European and USA(400v).
• CML (CONNECT MODEM to LINE) RELAY K1 is a switch designed to selectively connect the PSTN to system voice
communication path and fax communication path. In STAND_BY MODE and voice communication mode, it is con-
nected to TEL PART and FAX PART while communicating and dialing.
• CML Relay (K1): CML relay interfaces with T2(600:600) TRANS in communication mode.
• DC Impedance: DC impedance is determined in the DC Feeding Unit. It represents DC characteristic of the comput-
er connected through -48V DC power of the switch and lines. The DC characteristic of required by the communica-
tion standards of a number of countries is the DC resistance of 50Ω~300Ω to the current range of 20mA~120mA.
(value varies depend on countries).
• AC Impedance or Return Loss: AC impedance is determined by the peripheral circuits of T2 Transformer. It is the stan-
dard required for optimum signal transmission between computer and switch. When the AC impedance of the com-
puter for AC signal transmission and the AC impedance of the switch matches, the signal can be transmitted without
loss. Therefore, communication standards specifies the AC impedance of the computer and it implies the return loss.
The communication standards of each country, considering the characteristic of their lines, requires 600Ω or the return
loss of 14dB and higher against the AC impedance of Complex and the AC signals of 300Hz~400Hz. The AC imped-
ance of transformer changes depending on the load resistance, the core material, coil inductance and resistance, but
generally its characteristic against load resistance is considered.
TIP
RING
Repair Manual
3-26
ARS2
ARS1
ARS3
FG
<TEL_LINE INTERFACE CIRCUIT>
K1
to FAX
to TEL
Samsung Electronics