A new microphone Sound Detection System (SDS) is now available from Biosystems as an option on PosiChek3â„¢ computerized performance testers for air-supplied breathing apparatus. Designed to increase test precision by automating the primary audible alarm test, the SDS feature eliminates human error and makes the PosiChek easier to use. Biosystems, LLC, Bacou-Dalloz, Inc., Smithfield, RI.