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.