What is that on the roof?

It’s a mobile mast.

The large rectangular surfaces are the transmitting and receiving antennas which produce the “handy network”.

You can easily distinguish e-network and D-network. D-Net has almost always 4 antennas (90° coverage per antenna) and E-Net has only 3 antennas (120° coverage).

The small, rectangular top of it does not belong to the “handy net”. It’s a radio link. This mast is connected to another mast so that the only current does not need its own telephone cable or Glass fiber lines. It then splits the connection to the telephone network with its neighboring mast.