ADB Vol 1 fire detection

[xan]

For large dwelling houses, of 2 storeys,it recommends a grade B LD3 system. A grade 'B' system is decribed as one that comprises of fire detectors 'other than smoke and heat alarms'.Why is this?I don't understand why it is recommending a system that does not have smoke/ heat detectors, when other sizes of dwellings(bigger and smaller) have smoke/heat detectors.
Is it a misprint,or can someone please explain.

[Graeme]

because smoke and heat alarms are not the same as smoke and heat detectors.

[xan]

because smoke and heat alarms are the same as smoke and heat detectors.

  if you meant to say that they are not the same,it would now make sense! i.e. a smoke or heat 'detector' does not have an alarm(sounder) fitted in it,a smoke/heat alarm does.
If not please explain a bit more.

[Graeme]

sorry edited for typo

[xan]

Many thanks!It has fallen into place now
i knew it would be obvious,just had a long hard day!