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Television's evolution into a digital medium brings many benefits to operational broadcasting - as well as a few headaches.

For news, the headache has been on-air latency. Between the time that a person says or does something live in front of a camera and the time the viewer at home sees or hears that action, hundreds of milliseconds may elapse. Please note, that we are not referring to lip sync error - that is where the delay is different between the sound and the action, but equal delay. Equal delay does not normally cause any noticeable problem and the audience is unaware that it is taking place. Lips move in-step with audible speech.

Audio Delay Issues
Equal delay becomes a problem when on-air talent must monitor themselves off-the-air. Trying to listen to yourself with delays of only a few tens of milliseconds can destroy your ability to speak.

There are three paths that create delay in a broadcast news system:

1. Between the studio and the main transmitter
2. The use of satellite links to bring feeds from the field back to the studio
3. The change to COFDM to carry video from ENG trucks back to the studio

Any of these routes can introduce enough delay to make IFB unworkable.

When delay is great enough, typically more than half a second, it introduces another problem - sloppy cues. These are apparent to even a casual observer on multihop satellite feeds. But on a single satellite link, or even from a long studio to transmitter delay, the latency can cause a fast paced program to suddenly seem slow and sloppy.

PRO Channel
As the pioneer and principal supplier of PRO Channel based IFB systems for ENG operations, Modulation Sciences has been working on a solution to the problem of delayed IFB to on-air personnel working in ENG situations.

We found that since the problem has several sources, a systems solution, not a piecemeal one, was called for.

Our solution is based on proven PRO channel technology, the technology of choice when providing IFB to remote news activities; PRO channel offers many advantages over alternative technologies:

1. Being part of the stations own signal, there is no operating or per-use costs.
   
2. Coverage is greater than the station's video coverage because the technology is aural only, non-intercarrier.
   
3. Because of a television station's lower frequency and much higher power, there are far fewer coverage "holes" than with cell phones.
   
4. PRO channel is as reliable as your station. Cell phone service can fail when you most need IFB:
   
   1. It is subject to "blocking" in a crisis due to high user demand.
   2. It can lose power - most cell sites have only a few hours of backup power - compared with many TV stations that measure their emergency power capacity in days.
   3. In an emergency most cellular systems are subject to preemption by a wide range of local, state and Federal emergency service providers.
      
5. Mobile radio systems were the original carriers of IFB, but today private channels are nearly impossible to obtain - everything must be shared. In addition, without expensive trunking, coverage is seriously limited.

PRO Channel
Modulation Sciences introduces PRO-3 to solve your delay problems in ENG. PRO-3 offers two independent solutions to delay. Either of these solutions may be used standalone, or in conjunction with the other.

DELcor
Solution one:
Correct your delay. The DELcor feature provides an additional audio channel from the studio to the field for carrying undelayed program audio. Used in conjunction with proven CTCSS technology for selective calling to ENG trucks, this approach allows for seamless IFB to on-air personnel if most of the delay is between the studio and the main transmitter. Users will not even know that there is a delay on-air. This undelayed program audio is mutually exclusive with the SAP channel, although it does not employ the SAP channel, nor can it be received on conventional TV sets. Standard SAP may operate anytime that undelayed audio is not being supplied to the field.

DELiminate
Solution two:
Eliminate your delay. DELiminate is a unique application of squelch technology. Squelch is not new for IFB, but has always been unpopular because it totally silences the on-air person's earpiece - leaving them completely isolated from both program feed and interrupts from the director. The Modulation Sciences solution is unique in that it silences only the on-air signal that includes delayed speech, while allowing the director the freedom to send messages to specific individuals while they are on-air. This approach is essential when significant delay exists between the ENG/SNG location and the studio. This is the case with COFDM microwave truck to studio links and satellite feeds. Squelch technology allows the on-air person to take an in-cue from the program feed, then receive an out-cue countdown from the director.

Squelched PRO Channel may be used to solve any delay, regardless of where in the broadcast system it is being introduced. It will universally solve the problem of delay interfering with an on-air person's speech.