Bluetooth devices are designed to be mobile and require
battery power, conserving power is thus essential.
Once connected to a piconet, a Bluetooth device can be in
one of four power modes:
1. Active – device actively participates in the channel
2. Sniff – slave listens to the master at a reduced rate to uses
less power
3. Hold – only slave’s internal timer is running
4. Park – slave does not participate in any traffic but
occasionally listens to the master for time synchronization
and broadcast messages