Channel 3/4 output
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A channel 3/4 output was a common output selection for consumer audiovisual devices sold in North America that were intended to be connected to a TV using a radio frequency (RF) signal. This channel option was provided because it was rare to have broadcast channels 3 and 4 used in the same market, or even just channel 3 itself. The choice allowed the user to select the unused channel in their area so that the connected device would be able to provide video and audio on an RF feed to the television without excessive interference from a broadcast signal.
RF modulation was common on equipment deployed in North America. Other countries had the RF output for video equipment on different groups of frequencies. For example, equipment sold in Europe, South Africa and Hong Kong used UHF channels 30–39 for this purpose. Equipment sold in Japan used channel 1 or 2 (Channel 13–16 is for cable converters). With other channels being used for RF modulation function in other regions, channel 3/4 output is a misnomer for those regions.
In Australia, some manufacturers used the channel 3/4 output, while other manufacturers would use the UHF channels 30–36 for this purpose. It become common for VCRs sold in that market since the mid-1990s to use this output specification as well. The other common output frequency set in Australia was channel 0 and 1 on the VHF band throughout the 1980s. This was because most televisions that were deployed on the Australian market before model-year 1980 could not receive the UHF band.For years, the RF output for video recorders marketed for Australia used channel 0 or 1 on VHF bandwidth and these two channels were not usual on TV sets marketed for Asia/ Middle East,except for Sony Trinitron KV-2062E ( Asia model )which had the capability of receiving any frequency below channel E2. The S-VHS video recorder,HR-S6800EA made by JVC in 1992,was a model made for Australia and in terms of RF output it used VHF channel 0 or 1. In New Zealand,video recorders had RF output on either VHF channel 2 or 3 ( PAL B ).
Since 1982, VHS video recorders and VHS players ( 1984 onwards ) marketed typically for South and South-East Asia, featured RF output on PAL system, standard B, using VHF channel 3 or 4. Some models of course, featured output on PAL G using UHF channels 36 to 38.Usually these models were not recommended for use in Australia. VHS recorders made for Asia/ Middle East normally featured RF output on UHF channel E36 or E37 or even E38,and some decks offered selection between PAL and SECAM systems.
The VCR's ubiquity was responsible for making consumers familiar with RF modulation, which could explain its lasting popularity and use in all-digital media like DVD and video game consoles. A better explanation might be its familiarity and ease of use, along with legacy televisions, which could not readily support newer technologies like composite or S-video.
DVD's relatively later entrance to the marketplace means that most players after the early generations do not natively support RF modulation, instead relying on converters, which could also amplify the signal.
First- through early fifth-generation video game consoles commonly used this method to connect to the television, which was used as the audio and video device for the game. In many cases, an RF modulator was used to take the composite output from the game and modulate it before sending the signal to the television. Late fifth- through current eighth-generation video game consoles retain the ability to output through RF modulators, usually through a separately purchased adapter. Recently, some RF demodulators have been marketed on obscure online markets to allow channel 3 inputs from legacy devices to work on RCA composite in.