Creating a Bluetooth connection between two devices is a multi-step process involving three progressive states:

Inquiry– If two Bluetooth devices know absolutely nothing about each other, one must run an inquiry to try todiscoverthe other. One device sends out the inquiry request, and any device listening for such a request will respond with its address, and possibly its name and other information.

Paging (Connecting)– Paging is the process of forming a connection between two Bluetooth devices. Before this connection can be initiated, each device needs to know the address of the other (found in the inquiry process).

Connection– After a device has completed the paging process, it enters the connection state. While connected, a device can either be actively participating or it can be put into a low power sleep mode.

Active Mode– This is the regular connected mode, where the device is actively transmitting or receiving data.

Sniff Mode– This is a power-saving mode, where the device is less active. It’ll sleep and only listen for transmissions at a set interval (e.g. every 100ms).

Hold Mode– Hold mode is a temporary, power-saving mode where a device sleeps for a defined period and then returns back to active mode when that interval has passed. The master can command a slave device to hold.

Park Mode– Park is the deepest of sleep modes. A master can command a slave to “park”, and that slave will become inactive until the master tells it to wake back up.