Siemens SIMATIC S7-400 Reference Manual page 442

Glossary
Basic error limit
The basic error limit represents the operational limit at 25° C relative to the nominal range of
the analog module.
Baud rate
Speed of the data transmission (bps)
Central rack
An S7-400 consists of a central rack (CR) to which expansion racks (ER) can be assigned.
The central rack is the rack containing the → CPU.
Cold restart
→ Hot restart of the automation system and its user program after all dynamic data (variables
of the input/output image, internal registers, timers, counters etc. and their program sections)
have been reset to a predefined value.
A cold start can be triggered automatically (for example following power outage, loss of
information in the dynamic memory areas etc.).
Common mode voltage
Voltage common to all terminals of a group and that is measured between this group and any
reference point (usually ground).
Communication load
Load on cyclic program execution of a CPU caused by communication activities (PROFIBUS-
DP).
To prevent communication activities putting too much load on program execution, it is possible
to set the maximum permitted cycle load caused by communication in the parameter
assignment in STEP 7.
Communications processor
Programmable module for communication tasks, for example, point-to-point links.
Compensating box
Compensating boxes can be used when measuring temperatures with thermoelements
connected to analog input modules. The compensating box is a circuit for compensating
temperature fluctuations at the → reference junction.
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S7-400 Automation System Module Data
Reference Manual, Ausgabe 11/2016, A5E00850736-08