The Toshiba Strata CTX100. AMDS1A is a modem subassembly for the CTX100 telephone system. It allows your telephone system administrator to dial into your telephone system from a remote location over a CO line. The AMDS1A comes with a full year warranty. 1 per system, required if remote maintenance modem is needed. Mounts on the CTX100 with ACTU1A, ACTU2A or ACTU2A-S processor, or, CTX670 with BCTU1A processor. Not needed for CTX670 with BECU1A/BBCU1A processor which has a built-in remote maintenance modem.