UNIT, CONTROL; MUTING MODULE, 19.2-28.8 VDC. TYPE: MUTING MODULE, SUPPLY: 19.2-28.8 VOLT DIRECT CURRENT. MNFR DRG: 30162461 REV 0 ITEM: 8, MNFR DRG: BHD-4962A-470-1068-01 REV 0 ITEM: 8. FFT: THIS PART MUST BE PROGRAMMED BEFORE SHIPPING IF SOLD AS A SPARE PART OR RETROFIT; FOR LIGHT CURTAIN (MODEL: M4000)