Siemens SWT 3000 Equipment Manual page 311

When the unit is started, a self-test is carried out. A watchdog also monitors the functionality of the internal
Digital Signal Processor (DSP). If there are failures, the transmitter output and the relay outputs of the unit are
blocked. An overview of the functional units of the PU4 is shown in the following diagram:
[dwfunpu4-051011-01.tif, 2, en_US]
Figure 7-3
IFC Interface command module
PU4 iPS Internal power supply of the processing unit module
PU4 Processing unit module
LIA Analog line interface
DSP Digital signal processor
DLE Digital line equipment
LID Digital line interface
EN100 Ethernet EN100 module for IEC 61850
FOM Fiber-optic module
CLE Copper line equipment
ALR Alarm module
CSPi Central signal processing unit
SSI Serial synchronous interface
VF Voice frequency
Smart Communication, SWT 3000 Teleprotection, Equipment Manual
C53000-G6040-C605-1, Edition 03.2020
Functional Units of the PU4 Module
Processing Unit Module
7.1 Functions of the PU4 module
311