In the A.S.D. series there is at this time one part, used for monitoring the AC switch to make sure that it is working properly, an STCC08. This part will be discussed later in this presentation. The TPDV series is a very rugged industrial series of AC switches with voltages up to 1,200 V, and current ratings up to 40 A. Last in the list is the SCR series. SCRs are unidirectional switches, meaning they do not conduct in both directions of the AC cycle, they only conduct in one direction. SCR is an abbreviation for silicon control rectifier. ST manufactures both the standard and sensitive gate current trigger devices with withstanding voltages up to 1,200 V, available in both standard and high junction temperature devices with RMS current ratings up to 85 A.