I am an EST certified programmer/technician and I personally test all used parts before listing them.

Up for sale is an EST Edwards audio source unit unit for an EST3 system, the 3-ASU. This unit was fully functional when removed during a full fire system replacement, and was fully bench tested before being boxed up for this sale. This sale includes both the microphone  assembly AND the circuit board. Date code on the board is 21098 and the mic is 21102, as pictured. See photos. USPS priority mail shipping.