Giblets

Hi all, I'm very new to working on intruder alarms, this being my 3rd. I modified an existing Veritas 8 system by adding a PIR and a door contact. The alarm when in walk test mode is making two very short chirps at intervals of about 2 seconds. This isn't the normal chirps it makes when the Zone two device activates in walk test mode, but much shorter chirps. There are no lit tampers, and no lit faults. When it is chirping for zone activations, the shorter chirps are absent. Is the panel just reminding me it's in walk test mode, or is there some other unspecified (in the manual) problem I should be investigating. I'd be grateful for your assistance.