Muratec F-110 Field Engineering Manual page 58

4-4-3 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 overload pro-
tection in normal mode (between TIN and RING) and it uses ARRESTOR for 600V. However, arrestor's rated voltage dif-
fers from European and USA(400v).
• CML (CONNECT MODEM to LINE) RELAY K1 is a switch designed to selectively connect the PSTN to system voice com-
munication path and fax communication path. In STAND_BY MODE and voice communication mode, it is connected 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 computer con-
nected through -48V DC power of the switch and lines. The DC characteristic of required by the communication standards
of a number of countries is the DC resistance of 50 ~300 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 computer
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 com-
munication standards of each country, considering the characteristic of their lines, requires 600 or the return loss of 14dB
and higher against the AC impedance of Complex and the AC signals of 300Hz~400Hz. The AC impedance of transformer
changes depending on the load resistance, the core material, coil inductance and resistance, but generally its character-
istic against load resistance is considered.
TIP
RING
ARS2
ARS1
ARS3
<TEL_LINE INTERFACE CIRCUIT>
FG
Circuit Description
K1
to FAX
to TEL
4-25