FAQ:Will accessory decoders having extended addresses interfere with multifunction decoders?

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Short Answer

No

Longer Answer

The extended address partition for the multifunction decoder begins with values 192 – 231. The first byte of the 2 byte address can only contain values from 192 to 231. The second byte completes the address. The accessory decoder will only respond to packets if the first address byte of a nine or eleven bit address contains values from 128 though 291.

For example, the extended multifunction decoder address of 0128 transmitted by the command station would begin with the value of 192 in the first byte, followed by 128 in the second byte. So your accessory decoder would just ignore it. An accessory decoder needs to see a value between 128 and 192.

A more precise answer would be: The first two (or most significant) bits of an accessory decoder address must be 10.