"The DHI-VTNA1080B is designed to cooperation with
analog video doorphones and panels of DAHUA.
The device enables connecting and powering up to 8
devices via UTP (Cat. 5e) cables. For large systems the
devices can be connected in cascade. Up to 60 devices in
the cascade (480 panels in the system). Its using allows 
to create large surveillance system.
The ability to connect the signal and power together with
one UTP cable.
"