User manual

Last four
decades
Till to 2017
Now
Intercom development
 Analog system (4-
wire, 5-wire, 6-wire
and so on)
 More audio intercom,
less video intercom
 Simple function (only
support intercom)
 2-wire analog system
is the main choice
 Image quality is bad
(especially at night)
 Security level is low,
limited integration
function ( e.g. can not
view CCTV camera
mainly)
 Hikvision
released 2-
wire IP video
intercom