The Hail commands are set up so that you can detect other X10 controllers that are on the same powerline as your controller and so that you can tell the other controllers which house codes you are using. 

 The hail protocol has two parts.  First is the hail request (REQ) which asks for other controllers to identify themselves.  Second is the hail acknowlege (ACK), which is sent by the other controllers in response to the hail request

 The CM11A does not automatically respond to the hail request.  It must be done by software.  ActiveHome does this (or at one time did it - CWS) for the Windows based systems.

 The ACK should contain the house code that you have active.  If you have several house codes, you could reply with all of them, one after the other.

 The transmission for both ACK and REQ are one byte of function data in the standard hc:function format. See section 4.3 for the serial data buffer format.

 The REQ command appears to use any house code.  The ACK should have the house code set to the house code you are using.