Jessey, although your original query has been answered, I thought I would add my opinion as well.

When you speak of the X10 transmitter I assume you are referring to an X10 RF transmitter, right?

In which case, why not get rid of the X10 remote altogether, and drive an RF transmitter module directly with your 877? The RF protocol used by X10 is well documented (its actually the NEC IR protocol) and I could send you the URL(s). Besides the hardware being much simpler, you could send as many different commands and addresses as you wish without having to add more transistors.

Regards,

Anand