Disable 1992 Acura Legend Factory Alarm

Greetings - A few months ago, I had an mechanic install an ignition switch on my 1992 Acura Legend. The car had a 3rd party alarm, which he disabled. Upon changing the battery and attempting to start the car, the factory alarm now comes on (horns, flashing, etc.). When I turn the ignition key, the alarm continues and I cannot start the car. Now, every time I connect the battery, the factory alarm comes on and I cannot start the car. Can someone please assist?

Thanks