Finally had some free time today & I think I've gotten to the bottom of it.
It wasn't doing quite what I thought..... it wasnt actually going into alarm, even though it looked & sounded like it was.
Let me explain.....
TS700 panel + SD1 dialer + 2 x pyronix twin alert + 2 x SAB boxes + 12 x dual tech PIRs & 2 reeds.
SD1 is connected to Digicom outputs - SD1 'A' = 1, SD1 'B' = 2, SD1 'C' = 3.
These outputs are configured as 1 = 00 (Bell drive), 2 = 22 (Mains fail), 3 = 35 (Not Used)
The Twin alerts are driven from panel O/P 3 which is set up as 35 (Not Used)
The reason I thought that the system was going into alarm is that at the end of the part set timer the twin alerts go into alarm & the SD1 dials my mobile - I didn't check to see if the main bell box was triggered (it isnt).
Having removed a few wires & replaced a few O/Ps with 12V lamps things started to become clear.....
For some reason, on my panel, an output set to type '35' is triggered when the system is part set! The SD1 is being triggered on input 'C' which has no message associated with it (not input 'A' which is set up as intruder). The twin alerts are also actived.
Now, I'm not sure which version of firmware my panel is using & I know for certain that the copy of the installation manual that I have isnt the one which came in the box with the panel but do manufacturers change things like this during firmware updates?
The reason that the twin alerts where set to 'not used' was that I'd discovered an incompatibility between the twin alerts & the SD1 - if they are used on the same power supply - the SD1 will not dial when triggered. I'd solved this by fitting a separate PSU just to run these but had forgotten to enable them again.
Anyway, thanks to 'ALARM' for his suggestions .... have you ever met the output type 35 problem?
Adrian