Elgas ELCOR - Fig. 35 PS-M External Power Supply for the Internal Modem from PS-M Source

5 Installation and Commissioning
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the PS-M external intrinsically safe source. The S4-PWR2 module must be installed in SLOT 4.
Power from an external intrinsically safe PS-M source is fed to the PWR2 terminals.
In the event of a power failure, the modem battery (HB-03, HB-04, etc.) performs the power
backup function.
Fig. 35 PS-M External power supply for the internal modem from PS-M source