Appliance Control: Making Things Do Stuff - Smart Home Automation with Linux and Raspberry Pi - page 20

To transmit over two or more phases, you will need a coupler. This will listen for X10 signals on one phase of the
mains and replicate it on another. This can either occur in single unit (like the TF678) or require a separate device for
each phase that needs to be coupled (an FD10, shown in Figure 1-13 ).
Figure 1-13. The FD10, an interesting filter/coupler module, looking very uninteresting
Both of these coupler devices are, in fact, known as filter/couplers , meaning that instead of duplicating the X10
messages, they can filter them out entirely, thereby preventing the messages from leaking into your neighbors' houses.
And by extension, they can prevent your neighbors' X10 devices from controlling yours.
A bridge is a device that functions as a go-between for two different protocols. In this context, the protocols
invariably exist to bridge home automation systems such as from X10 to C-Bus or from X10 to UPB PulseWorx. Such
devices are useful for upgrading systems piecemeal or for controlling very specific devices that don't exist on your
system and/or for which no suitable software drivers exist. However, the cost involved in both the bridging device and
the original module would have to be very special to make it worth the money in most cases.
This, and many other exotic devices, are covered in Table 1-4 .