With an encryption box in place on the video/audio/data line, the only thing that needs to be secured is the dialing line. There are two options for securing the dialing line:
Dialing from the IMUX
One way to get around the security vulnerability associated with the dialing line is to bypass the dialing line entirely. A properly trained and certified technician can dial and initiate video-conference calls directly from the IMUX itself. To do this, the technician might have to disconnect and reconnect cables, sometimes located in remote areas [source: Security for Videoconferencing].
Dialing from the IMUX effectively secures the video-conference system, but requires time and special expertise to switch from nonsecure to secure mode and back again.
Dialing from the CODEC Menu Using an Optical Dial Isolator
For practical reasons, it's quicker and easier to initiate and dial both secure and unsecure calls from the video conferencing CODEC's on-screen menu rather than having to rewire the IMUX every time.
The problem is that the copper wire used in the dialing line produces data radiation levels that don't comply with the military's TEMPEST security standards. With the right equipment, however, it's possible to eliminate the data radiation problem without getting rid of the dialing line altogether.
This piece of equipment is called an optical dial isolator. Instead of transmitting data over a copper wire, the optical dial isolator uses fiber-optic cables that convert data into optical light streams that emit no data radiation at all. The isolator needs to be installed between the CODEC and the IMUX on the dialing line.
Using an optical dial isolator makes it easy for organizations like the government or the military to easily switch back and forth between unsecure and secure calls directly from the CODEC's on-screen menu. And with an encryption box already in place on the video/audio/data line, the video conferencing setup is now completely secure.
For more information about video-conferencing security and related topics, check out the links below.