The camera of the Alecto DVM-71 does not need to be always connected to wall power to function, as it is battery-powered. However, it does not hold a charge for an extended period when not plugged in. The camera unit is designed to be powered by batteries or an AC adapter, and it is recommended to keep it plugged in for continuous use to avoid battery drain. There is no specific mention of the battery life in the provided sources, but it is clear that the camera is intended to be used with a power source for optimal functionality. If battery life is a critical factor, it would be best to keep the camera plugged in to ensure continuous operation.

We use it in a two-storey house and it receives the signal well.

No, that's not normal. It should be very clear. Perhaps the connection is too far away.