SEGA Channel

SEGA Channel was a project developed by SEGA for the 16-bit Mega Drive and Genesis consoles, first announced in 1993. Starting in December 1994, the SEGA Channel service was provided to the public by Time Warner Cable and TCI, which later was acquired by AT&T during its cable acquisition spree that formed AT&T Broadband.

History
According to an informational piece broadcast over the channel, Stanley B. Thomas, Jr., former senior vice president of Time Warner, headed the service.

For a monthly subscription fee (usually $14.95 depending on location), along with a $25 activation fee, the subscriber would get an adapter, which plugged into the Genesis cartridge slot, and was connected to their cable television connection. The service would provide them with unlimited access to 50 games, selectable through an on-screen menu, with new games appearing every month. In its later years, this was changed to a selection of 35 games which rotated every two weeks. The games would be downloaded in about one minute and play just like the retail versions. These games were organized by genre, such as Action, Fighting, Adventure, and Family. Text-based instruction manuals for each game could also be accessed through a separate help menu download. Each month, there was a special theme with originally composed music, artwork and game categories.

Some unique content was released through the service:
 * Special "test drives" for up-and-coming titles were provided. In some, after a certain time limit (15 minutes), gameplay was terminated, and the player was returned to the menu. Other games had limited content; for example Primal Rage had only two characters playable.
 * Some games had to be altered due to transmission limits; such as Street Fighter II: Special Champion Edition only having six playable fighters and Sonic 3D Blast being split into two halves where the player had to enter a code they had received by finishing Part 1 to download and start Part 2.
 * Special modifications of existing retail games were made for SEGA Channel, the most popular of which was a special version of Earthworm Jim by Shiny Entertainment.
 * Some games not released in the United States were featured as "SEGA Channel Exclusives", such as Pulseman, Alien Soldier, Golden Axe III and Mega Man: The Wily Wars, among several others.
 * Cheats and tips could be accessed on the service and appeared while the games were downloading.
 * Throughout the service's life, contests were held, where players could win arcade machines, projection TVs, BMX bikes, etc.

The service was also available in Canada through Shaw Cable, in some parts of the United Kingdom on certain cable services, in Chile on the defunct Metropolis Intercom cable company, in Argentina on a national TCI branch, Cablevisión TCI, and in Australia on Austar and the now defunct Galaxy.

To provide SEGA Channel, a cable company would need to install new equipment into their headend, integrate service authorization into their sales center, and purchase the game adapters. Game adapters were manufactured by Scientific-Atlanta and General Instrument, with a cost to the cable operators of approximately $100 per unit. Additionally, many cable operators had to clean their broadcast signal in the head-end and all the way to "the pole" to ensure that the signal could be received. SEGA, a gaming company, thus played a major role in improving infrastructure for future digital cable services, as well as broadband Internet access and digital telephone services. At its peak, SEGA Channel was available to one-third of the United States and had 250,000 subscribers.

SEGA Channel was not a video-on-demand service per se; rather, as the service's name would suggest, it actually was a broadcast channel, similar to premium broadcast channels which (at the time) required a separate piece of addressable cable converter equipment to access. The program code for the on-screen menus and the 50 available monthly games was continuously broadcast as a sort-of "sequential access" RF signal. The menu system would be loaded into memory on power-up (which took about 30 seconds), and when a game was selected, the machine would "wait" for the requisite program code to be broadcast, then download it into volatile RAM. A downloaded game could not be garnered—upon hitting the adapter's reset button or powering off the console, it was erased from memory, and the user was required to download it again, if desired (The menu system would have to be re-loaded into memory also). Hitting the console's reset button while a game was loaded would perform normally.

This method of accessing program content was ahead of its time, and had only been tried once before, with Mattel's Intellivision platform. With all the electromagnetic "noise" inherent in older RG-59 coaxial cabling, downloading games could be problematic at times—such noise could and did disrupt transmission of binary images 4–32 megabits in size (as well as the menu system). If this were to happen, the download would fail, in which case the user would be required to reset the console and try again.

Special accessories for certain games, such as the Lethal Enforcers Justifier, posed a problem: users were warned not to leave them plugged in when they reset the console—otherwise, the SEGA Channel Adapter could be permanently damaged.

SEGA Channel ultimately ended due to the retirement of the Sega Genesis game platform and the difficult economics for the cable operators. The service ended on July 31, 1998, as the developers determined that the limited lifespan of the 16-bit technology was at risk due to the emergence of next-generation 32- and 64-bit technologies used by console developers Sega, Sony and Nintendo, coupled with the explosive growth of the Internet.

There were two different versions of the SEGA Channel Adapter, which were completely different in appearance—the first was manufactured by Scientific-Atlanta, and the second by General Instrument. Each adapter required a separate (included) 15-volt AC adapter to operate. Adapters were supposed to be returned to cable operators upon cancellation of the service; nevertheless, some of them still exist in the hands of collectors.

Technical information
The SEGA Channel signal originated in Denver, CO. It was carried over the Galaxy 7 satellite, located 91.0 degrees W longitude using transponder 1 with horizontal polarization.

The uplink signal was at a carrier frequency of 1.435 GHz and occupied 8 MHz bandwidth using QPSK modulation.

The downlink signal was at a frequency of 1.1 GHz and occupied 6 MHz bandwidth using QPSK.

Subscriber Loop
 * Occupied two 3 MHz non-contiguous channels
 * Data rate was 6 Mbit/s
 * Tunable to 68 different operating frequencies between 51 and 118 MHz
 * Bit error ratio was <10E-06
 * Used Quadrature Partial Response (QPR) modulation

QPR is a modulation scheme that uses a controlled inter-symbol interference. The receiver is capable of logically decoding the signal. QPR provides 20% better bandwidth performance than QPSK with only a minor increase in signal power.

This SEGA Channel Adapter allowed the customer to download the game selected in less than 1 minute. The adapter contained 4 MB DRAM, which held a game of up to 32 megabits (or 4 megabytes) in size. Once the game was downloaded, it worked exactly as if it were a cartridge. Sega also had ratings for each game and supplied the parents with a password (4 digit pin#) if so desired.