3/4Trk, 2Bri Board; Figure 4.13 Analog Trunk Board (3/4Trk) - Samsung OfficeServ 12 Service Manual

4.2.2.14 -5 V Constant-Voltage Supply Circuit
The PSU supplies -55 VDC and +5 VDC, and the constant-voltage supply circuit of the
base board supplies -5 VDC. The OfficeServ 12 system receives +5 VDC and generates
minus power by using the SMPS(Switching Mode Power Supply) technology. MC34063A
is used as the main component. -5 VDC power is mainly used as the minus power of the
3/4TRK board CODEC and the 2:4 hybrid circuit.

4.2.3 3/4TRK, 2BRI Board

An analog trunk board, 3/4TRK, or a digital trunk board, 2BRI, can be equipped on the
base board of OfficeServ 12.
4.2.3.1 Analog Trunk Board (3/4TRK)
The blocks of the 3/4TRK board are shown in the figure below:
TMC
(STL7053)
50P
CONNECTOR
2:4 Hybrid Circuit
A highway is a uni-directional transfer path for mass PCM data. Tx path and Rx path are
separately configured. When A/D or D/A conversion is performed by CODEC,
Tx conversion is performed separately from Rx conversion. Since a pair of copper wires
must accommodate Tx and Rx signals in a regular trunk line, a circuit where Tx/Rx signals
are combined is required. Four lines are combined to two lines when separated Tx/Rx
signals are combined. Therefore, this is called a 2:4 hybrid circuit.
© SAMSUNG Electronics Co., Ltd.
CODEC 2-to-4
(TP3057) Hybrid By-Pass
BASE
B'D

Figure 4.13 Analog Trunk Board (3/4TRK)

DC Loop Protec
Interface -tion
CID
RELAY
X3: 3TRK
X4: 4TRK
6P/6C
Modular
Jack
(X2)
19