The Powerhorns trigger on a one second cycle of power line signals. Takes about 4 cycles to trigger them and they sound for about 4 seconds after the cycle stops.
All Lights On, All Units Off to the House Code they are set to or an On, Off cycle to its Address.
The problem is the new SC1200A and the Radio Shack 49-1000MC. That was made by X10 for them.
Sends the two Light Address. The old model console only send one address and uses All Lights On, All Units Off.
Like A1, A2, AOn. Then A1, A2, AOff. Some versions of the Powerhorns did not trigger because the second address being sent messed up the Powerhorns seeing the cycle correctly.
Some sounded sporadically and some just take extra time to start triggering.
I have two Date Code 2010 ones that trigger then stop then start again. My 2004s just take extra time to trigger. A 2009 sounds one blast everytime the SC1200 is armed and the lights flash to indicate a successful arm.
All my findings are for the PH508 Large Powerhorn. I have no real data on the SH10A Small Powerhorns and how they work with a SC1200A.