Is BT Infinity 2 Home Hub 3 wireless router dual band?

The BT tech I have spoken with do not know. Dual band permits having two devices at two different speeds at the same time, whereas if it is not a dual band wireless router, the speed lowers to the speed of the slowest device (e.g., wireless g on smartphone, wireless n on laptop).

Is BT Infinity 2 HomeHub 3 wireless router dual band?

It's not dual band however you are wrong in saying every device will slow down to the slowest devices speed

Every device connects as quick as it can so one device may connect at 5 Mbps and another at 144 Mbps

The 144 Wont be slowed down to 5 Mbps all of the time

Dual band is usually taken to mean 2.4GHz and 5GHz frequencies at the same time.

My understanding is that it ( and most other wireless routers) will only use either 802n OR 802g at any time so if you have a g device it will default to 802g and therefore both devices will be slower.

Each device may be at a different speed but both/ all will use the same wireless standard.

If all devices are 802n they will all use the higher standard but may be at different speeds depending on device/distance/interference etc.

As Andrew says, dual bands are to do with two different wavelengths at the same time, but I think they both use the same standard at the same time..