Look at http://www.microchip.com/stellent/idcplg?IdcService=SS_GET_PAGE&nodeId=1824&appnote=en012050 No transformer is used. This is very timely as to where I am working at the moment. I am in the process of giving upon my current X10 installation. I am fed up with false turn on/off problems. I am replacing the computer controlled functions with fixed timers. There are a couple of instances where I will continue to use a remote control but things are going to have work better than my off-the-shelf system. Also check out Application note AN521. John Ferrell http://DixieNC.US ----- Original Message ----- From: "Anand Dhuru" To: "Piclist" Sent: Monday, November 28, 2005 6:02 AM Subject: [EE] carrier current signal injection > In most of the carrier current based systems, as in X10 transmitters, I > have seen a signal transformer at the mains end. I beleive this serves 2 > purposes; one of the windings generates the high frequency carrier signal > (usually around 120 KHz), and the other(s) couple the actual data, > modulated by the carrier, into the mains. > > Am I right till this point? > > The transformer does not provide any input-output isolation, as the input > and output sides often share the ground and so plays no role in the safety > of the circuit anyway. > > My question is, can the data, be modulated by a high frequency oscillator > (say using a 555) and fed into the mains thru' a capacitor, thereby not > having to use the transformer? > > I am trying to design my own X10 transmitter (I do know about the PL513 / > 523, but would still like to design my own), and was wondering about the > above aspect. > > Regards, > > Anand Dhuru > > > -- > http://www.piclist.com PIC/SX FAQ & list archive > View/change your membership options at > http://mailman.mit.edu/mailman/listinfo/piclist -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist