DIN EN 54-4:2015 pdf free download.Fire detection and fire alarm systems- Part 4: Power supply equipnent.
If the PSE is housed in other equipment, manual controls, fuses, calibration elements etc. for disconnection and adjustment of the power sources shall be accessible only at AL3 or AL4 of EN54-2orEN54-16,orbytheuseofatoolorkey. The PSE may be distributed in which case 4.2.5.2 to 4.2.5.7 shall apply. For each main power source and each standby power source the manufacturer shall
provide the output specification, including maximum power loading, and shall provide the possible configurations for powering connected equipment. For each specified configuration, one or more main power sources shall be associated with one or more standby power sources, such that connected equipment remains powered in the event of failure of any and all main power sources. If the PSE has more than one main power source, in the event of failure of a main power source, current may be drawn from one of more
standby power sources. The PSE shall be capable of recognizing and signalling short circuit or interruption in transmission paths between its components within 100 s of the occurrence of the fault. The PSE shall provide at least a common fault output for the faults mentioned in 4.2.1.9.a) to d). and 4.2.5.4. This output signal shall also be given if the PSE is de-energized. If the PSE is housed in a separate cabinet or cabinets, or cabinets associated with other fire detection and fire alarm system equipment, manual controls, fuses, calibration elements etc. for disconnection and adjustment of the power sources shall be accessible only by the use of a
tool or key. The PSE design may be based on one or more of the following in order to fulfil requirements of this European Standard.
a) The equipment may be wholly or partly controlled by software. This software may have been developed and tested by the manufacturer, or may have been developed and tested specifically for the PSE by third parties under the control of the manufacturer.
b) Parts of the software may be common to other applications, and supplied to the manufacturer by third parties (e.g. operating systems, task scheduler, memory handler). In this case, the manufacturer may not have access to full design information, including
software source code. c) The equipment may contain software-controlled modules that are supplied to the manufacturer by third parties, e.g. switch-mode voltage convertors, memory. In this case,  the manufacturer may not have access to full design information, including that for the embedded software. d) The equipment may contain software-configured electronic components, e.g. programmable logic devices. If any of the above applies, this shall be documented by the manufacturer (see Annex A) and the
PSE shall comply with the requirements of 4.2.6.2 to 4.2.6.5, where applicable. DIN EN 54-4 pdf download.