X10 Control Question

["hi ho" <someone@xxxxxxxxxxxxx>]

I have an automation controller that can control powerline X10 devices by
connecting a Power Line Interface (PL513 or TW523) with a supplied cable
with RJ11 connectors on each end that plug between my automation controller
and powerline interface module.

Now the query, what serial communication protocol is used between the PL513
and my automation controller.  Reason is that I do not really want to
control using the powerline option due to reliability issues - rather
connect say a Rain8 X10 device (that is normally connected to the powerline
via TW523 like my automation controller) directly by cable to my automation
controller.  Indeed can you daisy chain say two Rain8 or more X10 devices
(with different X10 addresses) on a single cable like you can RS485 serial.

BTW - the Rain8 is a device that provides 8 analogue switched outputs under
X10 control for sprinkler control.  It seems logical to my mind that you
should be able to directly connect the automation controller and the Rain8 -
as both use the Powerline Interface Modules to communicate via the power
line carriier.

Hope some expert in X10 can help.