How many Bluetooth devices does the U3 support?

Paired/stored devices: The U3 can store up to 30 devices in its memory. (For comparison, the U2 supports up to 15 total devices, with no more than 4 Bluetooth devices among them.)

Simultaneous active connections:

The U3 can connect to up to 3 BLE (Bluetooth Low Energy) devices at the same time, OR

It can connect to 1 classic Bluetooth (BT) device at a time.

Important: The U3 cannot connect to 2 classic BT devices simultaneously. If you need multiple active connections, use BLE devices instead.