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Sound-in-syncs

Sound-in-syncs is a engineering topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Sound-in-syncs rather than just read about it. In short: Sound-in-syncs is a method of multiplexing sound and video signals into an analogue television channel designed to carry video, in which data representing the sound is inserted into the line synchronising pulse of the video waveform. This was used on point-to-point links within broadcasting networks, including studio/transmitter links.

Key takeaways

  • Sound-in-syncs belongs to engineering; place it in that map before memorising details.
  • Learn the definition first, then one example that makes the definition concrete.
  • Connect Sound-in-syncs to a quantity you can measure, compute or draw — that is where exam questions come from.
  • Reproduce the core statement of Sound-in-syncs from memory before moving on to harder problems.

Reference excerpt

Sound-in-syncs is a method of multiplexing sound and video signals into an analogue television channel designed to carry video, in which data representing the sound is inserted into the line synchronising pulse of the video waveform. This was used on point-to-point links within broadcasting networks, including studio/transmitter links. It was not used for broadcasts to the public.

History The technique was first developed by the BBC in the late 1960s. In 1966, The corporation's Research Department made a feasibility study of the use of pulse-code modulation (PCM) for transmitting television sound during the synchronising period of the video signal. This had several advantages: it removed the necessity for a separate sound link, reduced the possibility of operational errors and offered improved sound quality and reliability.

Awards Sound-in-Syncs and its R&D engineers have won several awards, including:

The Royal Television Society's Geoffrey Parr Award in 1972 A Queen's Award for Enterprise in 1974 In 1999, a Technology & Engineering Emmy Award

Versions

Original mono sound-in-syncs In the original system, as applied to 625 line analogue TV, the audio signal was sampled twice during each television line and each sample converted to 10-bit PCM. Two such samples were inserted into the next line synchronising pulse. At the destination, the audio samples were converted back to analogue form and the video waveform restored to normal. Compandors operating on the signal before encoding and after decoding enabled the required signal-to-noise ratio to be achieved. As the PCM noise was predominantly high-pitched, the compandor only needed to operate on the high frequencies. Also, the compandor only operated at high audio levels, so that modulation of the noise by the companding would be masked by the relatively loud high-frequency audio components. A pilot tone at half the sampling frequency was transmitted to enable the expander to track the gain adjustment applied by the compressor, even when the latter was limiting. Following successful trials with the BBC, in 1971 Pye TVT started to make and sell the sound-in-syncs equipment under licence. The largest quantities went to the BBC itself, to the EBU and to Canada. Smaller numbers went to other countries including South Africa, Australia and Japan.

Ruggedised sound-in-syncs A ruggedised version of the system was developed, which provided about 7 kHz audio bandwidth, for use over noisy or difficult microwave paths, such as those often encountered for outside broadcasts.

Stereo sound-in-syncs Later systems, developed in the 1980s, used 14-bit linear PCM samples, digitally companded into 10-bit samples by means of NICAM-3 lossy compression. These were capable of carrying two audio channels and were known as stereo Sound-in-Syncs.

ITV sound-in-syncs The ITV network used coders and encoders produced by RE of Denmark. The two variations of Sound-in-Syncs used by the BBC and ITV were not compatible. The terms DCSIS or DSIS was commonly used in ITV to describe dual channel Sound-in-Syncs. Very often material carried was not stereo, but dual mono.

Notes and references

See also VIMCAS

Further reading Waveform Specification of the BBC Sound-in-Syncs Equipment, EBU Review, 121A, June 1970. Chorley, J.M. and Shorter, D.E.L. (1970), P.C.M. Sound-in-Syncs: Operational Systems for Video Distribution and Contribution Networks, IEE Conference Publication, No. 69, 1970 International Broadcasting Convention Dalton, C.J. (1968), The Distribution of Television Sound Signals by PCM Signals incorporated in the Vision Waveform, IEE International Broadcasting Convention, September 1968, Vol. 46, Part 1 Sanders, J.R. (1967), Pulse sound: a system of television sound broadcasting using pulses in the video waveform, BBC Engineering Monograph, No. 67, May 1967 Sanders, J.R. (1968) Pulse-code modulation for high-quality sound signal distribution: Incorporation of the sound signal in the video signal. BBC Research Department report (PDF) Shorter, D.E.L., Chew, J.R., Howarth, D. and Sanders, J.R. (1968), Pulse code modulation for high-quality sound signal distribution, BBC Engineering Monograph, No. 75, December 1968 Shorter, D.E.L. (1969), The Distribution of Television Sound by Pulse-code Modulation Signals incorporated in the Video Waveform, EBU Review, No. 113A, February 1969

Worked examples

Example 1 — a first encounter with Sound-in-syncs

Start with the simplest possible case. Write down what Sound-in-syncs claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In engineering, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Sound-in-syncs before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Sound-in-syncs ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Sound-in-syncs

In research
Sound-in-syncs appears in engineering research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry
Engineering practice reuses Sound-in-syncs in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom
Sound-in-syncs is common in secondary-school and first-year university syllabi. It links to neighbouring topics BBC Research & Development, Broadcast engineering, Sound, so understanding it makes those chapters shorter.
In everyday life
Look for Sound-in-syncs outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.
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How to study Sound-in-syncs in 20 minutes

  1. Read the reference excerpt below once, without taking notes.
  2. Close the page and write down what Sound-in-syncs means in your own words.
  3. Compare your version with the excerpt and mark what you missed.
  4. Work through the three examples above with pen and paper.
  5. Explain Sound-in-syncs out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Sound-in-syncs in simple terms?

Sound-in-syncs is a method of multiplexing sound and video signals into an analogue television channel designed to carry video, in which data representing the sound is inserted into the line synchronising pulse of the video waveform. This was used on point-to-point links within broadcasting network…

Why does Sound-in-syncs matter?

Because it connects several engineering ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Sound-in-syncs?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Sound-in-syncs.

Tags

  • BBC Research & Development
  • Broadcast engineering
  • Sound
  • Television technology
  • Video formats

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