BS EN 54-12:2002 pdf download – Fire detection and fire alarm systems — Part 12: Smoke detectors — Line detectors using an optical light beam 4.8 Limit of compensation The detector shall emit either a fault or alarm signal at the limit of compensation for the effect of a slowly changing response (signal). Since it is practically impossible to perform tests with very slight increases in smoke density, an evaluation of the detector’s conformity shall be made by analysing the circuits/software and/or by physical tests and simulations. 4.9 Additional requirements for software controlled detectors 4.9.1 General For detectors which rely on software control in order to fulfil the requirements of this standard, the requirements of 4.9.2 and 4.9.3 shall be met. 4.9.2 Software design In order to ensure the reliability of the detector, the following requirements for software design shall apply: a) the software shall have a modular structure; b) the design of the interfaces for manually and automatically generated data shall not permit invalid data to cause error in the program operation; c) the software shall be designed to avoid the occurrence of deadlock of the program flow. 4.9.3 The storage of programs and data The program necessary to comply with this standard and any preset data, such as manufacturer’s settings, shall be held in non-volatile memory. Writing to areas of memory containing this program and data shall only be possible by the use of some special tool or code and shall not be possible during normal operation of the detector. Site-specific data shall be held in memory which will retain data for at least two weeks without external power to the detector, unless provision is made for the automatic renewal of such data, following loss of power, within 1 h of power being restored. 4.10 Fault signalling A fire alarm signal shall not be cancelled by a fault resulting from a rapid change in obscuration (in accordance with 5.6) or by a result of the limit of compensation being reached (in accordance with 4.8). 5 Test methods 5.1 General 5.1.1 Atmospheric conditions for tests Unless otherwise stated in a test procedure, the testing shall be carried out after the test specimen has been allowed to stabilize in the standard atmospheric conditions for testing as described in EN 60068-1 as follows: temperature: 15 °C to 35 °C; relative humidity: 25 % to 75 %; air pressure: 86 kPa to...
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