150 Chapter 13—Multiple D24s & Video Sync
D24—Owner’s Manual
Terminating BNC Video Sync Distribution
When a video sync signal is distributed via BNC cables, it must be terminated correctly.
Normally, termination is applied at the last device connected, although it depends on
the distribution method being used. The D24’s VIDEO 75Ω ON/OFF switch allows the
D24 to be connected in a variety of ways. The following examples show three ways in
which a video sync signal can be distributed and how termination should be applied.

Video Sync Distribution Box

In this example, a dedicated video sync distribution box is used to supply a video sync
signal to each device individually. Termination is applied on each device.

Bus Distribution

In this example, the video sync signal is distributed via a common bus. Termination is
applied at the last device only.

Daisy Chain Distribution

In this example, the video sync signal is distributed in a daisy-chain fashion, with each
device feeding the video sync signal on to the next device. Termination is applied at the
last device only. This method of distribution is not recommended for larger systems.
Device-A
Termination = ON
Device-B Device-C Device-D
Termination = ON Termination = ON Termination = ON
VIDEO OUT
(BNC)
Video sync
master Video sync
distribution box
Video sync slave Video sync slave Video sync slave Video sync slave
VIDEO IN (BNC) VIDEO IN (BNC) VIDEO IN (BNC) VIDEO IN (BNC)
Device-A
Termination = ON
Device-B Device-C Device-D
Termination = ON Termination = ON Termination = ON
Video sync
master
Video sync slave Video sync slave Video sync slave Video sync slave
VIDEO IN (BNC)
VIDEO OUT (BNC)
VIDEO IN (BNC) VIDEO IN (BNC) VIDEO IN (BNC)
Device-A
Termination = OFF
Device-B Device-C
Termination = OFF Termination = ON
Video sync
master
Video sync slave Video sync slave Video sync slave
VIDEO IN
(BNC)
VIDEO OUT
(BNC)
VIDEO OUT (BNC)
VIDEO IN
(BNC)
VIDEO IN
(BNC)
VIDEO OUT
(BNC)