Question:
I had to reinstall my smoke detector 521-BXT (2 wires, system is DSC) - does polarity (+/-) matters ? And if yes how can I set it right ?

Also the smoke detector does not have any test buttons - how can I make sure it works ?

Answer: Yes, polarity matters! Check out the installation guide diagram on page "ii" of the manual. You must hook up your two wire smokes that way.

This is a commercial grade smoke detector. Only the following models are directly compatible (UL approved) with the DSC 5010:

429AT 521B/BXT 521NB/NBXT

The 521 BXT generates a "CleanMe" signal that will not be interpreted by the DSC equipment. You'll require an ESL 505 module to interpret that signal. Check out the compatibility chart here:

http://www.sentrol.com/products/pdf/ESL_comp_index2002.pdf

Testing the equipment requires a magnet or UL approved canned smoke. Instructions for testing should be with the detector.