The interconnection to your security system employs a relay that's not compatible with the Kidde units. You'll have to obtain the Kidde relay module for this. This brings up a very important point. Your security system should be using compatible smoke detectors instead of interfacing the AC units as you have. When you lose power, the smoke alarms will continue to work, but the relay module won't operate so the security system won't activate. The relay module is available from Home Depot. The part number is XXXXX
You'll also have to contact your security provider to interface the new relay module.
I would strongly suggest you disconnect the interface wire on your smoke alarms until you replace the relay (or if you know where the relay is, disconnect the interconnection wire). You may damage your smoke alarms if the old BRK smokes didn't have battery backup. In this instance the BRK units will be using 120VAC to "switch" the relay. Your new Kidde units are using 9VDC.
I would suggest you talk to your alarm people about tying in system supervised smoke detectors. This provides an advanced level of security foryour family.
As for the BRK alarms, the older models didn't have battery backup and I doubt that the new ones would be compatible with the existing relay.
Ok thanks for your help. The old smoke alarms were tied into the alarm and were monitored. I'll just get them to get the system up to snuff with the new alarms.