The main application for extended messages is to set certain wall switch and lamp modules to defined brightness levels without having to ramp down from full-on first. Extended messages are also used by some higher end devices for “scenes” that allow a single X10 command to ramp multiple dimmers to different pre-set brightness levels.
Extended messages deviate from the standard X10 message format in that they extend over 31 powerline cycles rather than 22 cycles. Normal commands are sent twice, with the exact same bit pattern duplicated in the second half of the message. Repeaters take advantage of that by receiving the first half, and re-transmitting it overlaid in bit-sync with the second half.
Extended messages are sent only once by some controllers, such as the Ocelot or the Leviton 16400 with a scene keypad. Even though it is possible to receive that command, repeating it would require that no other command be transmitted closely following the original extended message. Otherwise, there would be a collision between the two commands, and both would be corrupted.
Some controllers, such as the CM15A and HomeVision, solve that problem by sending extended messages twice with no intermediate gap, just like normal commands. While older repeaters have trouble with extended messages, some newer repeaters, such as the Leviton HCA02-10E, are capable of handling these “doubled” extended messages properly. A forthcoming firmware update will support “doubled” extended messages in the XTB-IIR.
Jeff
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Topic: Extended Messages and Repeaters (Read 10002 times)