The first time you connect a wireless ANT+® or Bluetooth® sensor to your Garmin® device, you must pair the device and sensor. After they are paired, the device connects to the sensor automatically when you start an activity and the sensor is active and within range.
when strap is connected it turns off the wrist HR automatically. I use very basic HRM1 i bought 3 years ago on amazon for $15 and it works fine. Every time it starts to act off,i ts time to replace battery(done it 3x in 3 years) . Also what happens every now and then is that i have to take out the battery, put it back, delete the device and pair it again. But yeah my has Ant so maybe there is something to it as well.