TV Norge, a network in Norway wanted a system that allowed their local stations to be controlled from the central station (allowing program inversion from central to local). They have a mix of analog/digital uplinks and are supplying signals both in digital and analog format.
In order to achive their goals, Tv Norge tried 3 different systems:
It was found audible and not reliable enough, because program material can easily contain DTMF (on commercials, for example).
2. Systems using empty lines in the video signal
Those signals disappeared as a side effect of digital compression.
3. Ancillary data channels existing only in digital uplinks.
Those were not generally available and were non-synchronous with the video signal
After the initial trials at their Oslo premises, it quicky become evident that the LARSEN RCT1/RCR1 system was the only one permitting:
Bypassing multiple video/audio compression used in their up/downlinks (D2MAC/DVB compatible)
Ensuring sync between video and control
The non-audibility of the control signals
Close to 100% reliability
The RCT1/RCR1 system uses digitally modulated analog carriers placed either at the top or the bottom of the audio spectrum to allow remote control of distant stations from the main station. It is essentially non-audible and the performance is repeatable.
It can remotely close contacts, send serial commands to machines from the receiver interface, do stereo-mono-bilingual switching, and even transfer files via the air to a computer attached to the receiver. Moreover, each receiver may be addressed individually or in-groups.
It is controlled by means of supplied Windows™ software.
The same hardware with different software was even used to implement an automated audit system to BBC Radio Five Live (see the article on our WEB site).