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4.5. Operating behaviour of the monitoring equipment
For the evaluation of the monitoring a superior control system, which is in accordance with the functional safety re-
quirements of IEC/EN61508, must be available. The control system must be capable of carrying out a fault analysis
according to the capacity of failure in connection with the operational condition of the sounder. The following depend-
encies between operational condition and capacity of failure are therefore possible. Please also take note of the pos-
sible switching status as shown in
It is assumed that the monitoring equipment is supplied with operational voltage at least 1s before switching the
sounder channel on and the condition of the alarm output is checked 0.5s after switching on at the earliest. This pro-
cedure is an integral part of the automatic test function, as described in section
a) Switching on the power supply of the sounder channel in a fault free condition results in the controlling of the
MOS relay (the output of the MOS relay is low resistance). This takes place with a delay of 0.2 seconds. This
is on the condition that a tone has been selected with help of the DIP switch for the tone selection or a re-
spective tone has been activated from the 'external tone selection' and the monitoring circuit is attached to
the power supply. If the capacity of failure has not become low-resistance after this time then a fault has oc-
curred in the supply of the sounder channel, in the sounder channel itself or in the monitoring equipment. If
the capacity of failure is already low-resistance before hand, then there is a conductor end or a malfunction in
the monitoring circuit.
b) If the operational voltage of the sounder channel is switched off, a fault message is given via the fault alarm
relay with a delay of 0.2s to 2.5s. With an uninterrupted sounding, a reaction of the alarm relay of >0.2s can
be expected. The longer delay can result in tonal pauses in uninterrupted sounding when switching off.
c) If tones are automatically ended by the sounder (such as with tones 26 and 98, for example) then a fault is
also reported after 4s. In this case, the control must take into account the procedure of the tonal generation
(60s) and reset it.
d) If, during operation of the sounder channel, it is the case that the sounder remains off without the operational
voltage for the sounder channel being switched, the alarm output becomes high-resistance after a maximum
delay of 4s and therefore a fault is reported.
e) The minimum duration of an alarm is 5s. Only after this time, e.g. in the case of a short-term error, will the
diagnosis circuit return to the normal monitoring mode.
4.6. Time dependencies
Fig. 8
Function time diagram
Tone
Operational voltage
Sounder channel
Operating voltage
Monitoring circuit
Alarm output
* depending on the tone
for non-interrupted tones 0,2s
for long tone intervals up to max.
2,5s
** valid only for the independent
ending of tones 26 and 98
