I'll interject also that the 2-way X10 modules really do not add much value to an X10 system unless you have a special use case or reliability is of critical importance (in which case, you may want to consider using something other than X10 anyway). Polling and receiving an X10 module status is slow, and if you poll often, creates a lot of traffic. Extra traffic also decreases reliability in the presence of "non-polite" transmitters that don't implement collision avoidance. 2-way X10 modules have a transmitter in them, and every transmitter also attenuates powerline signals a bit, so having every module be a 2-way module would further increase likelihood of X10 signal issues.
It's often better to just keep track of the last state for a given module by listening to commands on the powerline. AHP does this. For something like a lamp module, the only time the state changes locally with no command on the powerline is when someone changes the module's state from OFF to ON by toggling the switch on the lamp. An LM14A also doesn't report this status change immediately; it has to be polled. I can see more value for 2-way communication in a device like a wall switch module, which is primarily controlled locally. There were Leviton DHC, ACT A10, and SmartLabs SwitchLinc modules that would report a status change immediately when controlled locally, but the X10-compatible ones are all discontinued. They also all required a neutral connection.
