Figure 5-3 Jack - Siemens SIMATIC S7-400H System Manual

To connect an auxiliary voltage to the "EXT. BATT" input, you require a cable with a 2.5 mm ∅
plug as shown in the figure below. Observe the polarity of the jack.
Figure 5-3
You can order a jack plug with an assembled cable from the using order number
A5E00728552A.
Note
When you replace a power supply module and want to backup the user program and data
stored in RAM while doing so, you should connect an auxiliary power supply to the "EXT.
BATT." input as mentioned earlier.
S7-400H
System Manual, 09/2007, A5E00267695-03
Jack
Installation of a CPU 41x–H
5.1 Control and display elements of the CPUs
43