Broadcast Systems and Television Standards

PAL

PAL (Phase Alternating Line) was created by Walter Bruch in Germany, 1963. PAL consists of 576 visible line and uses 50i or 25p. PAL's picture resolution is 720 x 576 and is colour television. It's widely used across Europe, Australia and Africa. PAL uses interlaced frames (lines update on one line, odd lines update on the next frame) as this gives a smoother motion. Lastly PAL standards automatically cancels hue errors by phase reversal so therefore a tint control is unnecessary.

NTSC

NTSC was created by the National Television System Committee in 1941 and recreated in 1953. NTSC is expressed by 480 visible line and value 60i or 30p. It's picture resolution is 720 x 480 and is colour television. It's extensively used in the North and South America, South Korea, Japan and the Philippines. NTSC is interlaced therefore each frame is scanned in two fields of 262 lines and then is further combined to display a frame of 525 scan lines and it's receivers have a tint control to perform colour correction manually.

SECAM

SECAM (Séquentiel couleur à mémoire) was created by Henri De France in 1967. SECAM subsist 625 visible lines and avails 50i or 25p. It's picture resolution is 720 x 576 and is colour television. It's broadley used in Europe, Australia and Africa. SECAM Splits colour on the broadcast which is better for colour reproduction but weakens the signal if one of the three connections is lost, therefore is a downside. SECAM is an Anolog television system and uses memory to store lines of colour information to eliminate the colour artifacts found on systems.

PAL Vs. NTSC

• Pal has a greater resolution than NTSC and is more widely used. 
• PAL provides a colour tv standard for the european picture frequency of 50 feilds per second.
• Both give the illusion of fluid motion.
• PAL has a closer frame rate to film and is less likely to suffer from issues that may be caused during frame rate conversion.
• PAL systems cancel out Chrominance phase errors by using 1H delay line which results as a lower saturation (less noticeable to the eye than NTSC hue errors).
• Pal has a 20% higher resolution.
• DVD's are mastered in both and coded for specific geographicsl regions with regards to playback compatibility.
• PAL swaps the phase of the colour information on alternative lines which is used to drive a phase locked sub-carrier recovery system within the receiver.

SECAM Vs. PAL

• Countries using SECAM have DVD's mastered in the PAL video format.
• SECAM is an earlier attempt at compatible colour television.
• SECAM transmissions are more robust over longer distances than PAL.
• SECAM colour signal remains present although at reduced amplitude thus has a stronger cross colour.
• SECAM receiver needs a delay line but unlike PAL it's not possible to build a receiver without one.
• SECAM frequency modulates the sub-carrier and only sends one set instead of two.

Television standards

Sky:Satellite (BSkyB)
Sky was originally seperate from British 
Launched: 2nd November 1980
Defunct: 5th feb 1989 by 
HeadQuarters: London,UK
Key Person: Nicholas Ferguson

sky is expensive in comparision to other competetors but has a wide variety of channels and being the oldest satellite company, has the highest amount of viewers who have subscribed to their packages reaching over 10 million.
It also includes the following services:

• Premiership Football
• Sky Multichannels
• Sky Digital
• HD
• 3D
• Sky Plus

satellite Broadcast  but due to high demands both were sufferening from loss of strong competition struggling finacially and decided to reorginize a new company

Freeview Terrestrial
Launched: 30th October 2002
HeadQuarters: London,Uk
Key Person: Ilse Howling
Freeview is a paid standard tv licience
you dont get as many channels but it a lot cheaper
The service cost is offered at no charge as well as a stronger signal that doesn't break up as much as the analogue tv.
It provides a selection of different channels and picks up via the free service as oppose to the analogue which is now disconnected.

Virgin Cable
Founded: 6 March 2006
Key Person: James Mooney
HeadQuarters: New York and Hampshire, UK
Products and services 
HD channels
On demand
3D
Although Richard Branson owns virgin as a whole James Mooney is the Chairman of Virgin Media
Virgin also pays money to use sky movies which incourages people to purchase their offers has a wide variety of movies to catch up on as well as live tv 
4OD free as long as your not watching it on your computer live 

• Cover the following; satellite, sky terrestrial freeview, digital , cable,bt virgin internet tv 4OD, itv player
• Add images where applicable

On demand Television provides a good service as your able to watch it whenever and wherever you want on any portable electronic as long as it's connected to the wi-fi.You are given the option of more services with a broader variety ranging from od series throughout to the most recent series seen on tv. On the other hand there is also disadvantages to demand television such as the inconvenient adverts that your not able to skip. You always need a strong internet connection otherwise when your wi-fi drops out you automatically loose connection.