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


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