Larry,

Not to be impertinent here, but are you sure there is an ALL UNITS ON command? It'd have to be an extended data command, because all X-10 command codes are already defined and none of them is ALL UNITS ON.

All Lights Off 0110
Status Off 1110
On 0010
Pre-set Dim (1) 1010
All Lights On 0001
Hail Acknowledge 1001
Bright 0101
Status On 1101
Extended Code 0111
Status Request 1111
Off 0011
Pre-Set Dim (2) 1011
All Units Off 0000
Hail Request 1000
Dim 0100
Extended Data Transfer 1100

As far as I know, the IR543 is capable of sending all these commands, but many of them would be fairly useless (ie Hail Request, Status Request, etc) with an IR543.

John Galvin