You have to have a sounder , doesn't have to be 120db and the keypad won't give you an intruder tone
Personally I would want the internal sounder and bell delay external sounder
Only problem you might get is the resolution may keep trying to switch u til it finds a compatible one but you have switch to make it stick to source output
That's weird man
On hkc , if the system working on app, customer would get a notification "engineer here"
If system is set you can't access, if system unset you still get that notification , even with engineer access always you get internal bells locally and remotely until you press a key
So customer would hear something
Codes can't be viewed though