Assuming same power supply the 0v is the same
tr is just that and isto inform the pnal of tamper from the bell. Diff bells report/detect different things
testing should be clear when in normal state, should be in alarm when attacked
Put your meter on ac volts
Pos probe to 12v dc
Neg probe to good mains earth
Check reading with mains on and mains off
Ensure meter isn't in current probe position
I only know the hkc GSM option that is 4g and WiFi combined
Plus the paths are then monitored separately. Polling rates are the thing to consider here. Just cos WiFi is available or 4g signal etc doesn't mean the alarm can transmit data. Proper pro systems poll at regular intervals. Ie grade 4 comms every 30 seconds grade 2 comms every 24 hours.
The faster the poll rate the quicker a failure is reported. Plus if a GSM jammer and line cut is performed the quicker an alarm can be generated.