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CoCo 1 & 2

From CoCopedia - The Tandy/Radio Shack Color Computer Wiki
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Hooking Up the CoCo 1 & 2

The CoCo 2 is very similar to the original TRS-80 Color Computer in its capabilities. Most significantly for this section, they have the same connections to the outside world.

What's in the Case?

The CoCo 1 & 2 are pretty simple computers as shipped. Inside they have a Motorola 6809E microprocessor, 4 - 64K of dynamic RAM, and a built-in keyboard. On the right side is the expansion slot, where you can plug in Program PAKs (cartridges housing a program in a ROM chip), disk controllers, and other hardware expansions. On the back are DIN sockets for the serial port (often referred to as the "bit-banger"), the cassette port, and two joystick interfaces. There is also an RCA jack for the RF modulated audio/video output and a switch to select between channels 3 and 4.

The only peripheral strictly necessary for interactive use of an unmodified Color Computer 1 or 2 is a television set. The television is the CoCo's video monitor, and the TV's speaker plays the sounds the CoCo produces. The CoCo's video signal is RF modulated, which just means that it is converted to a radio frequency signal so that it can be injected through the TV's antenna connector to the TV's tuner, which is designed to pick up a radio frequency signal. The CoCo was designed in a time before the availability of cheap VCRs and DVD players demanded that TVs provide non-RF composite video inputs. The antenna connector was the only way to get a signal into most of the available TVs at that time.

But all this conversion of the video signal to RF and back again degraded the signal and added noise to the picture. Don't expect a razor sharp display like what you're used to on your modern computer monitor. The CoCo 1 & 2 can be modified to supply a non-RF video signal, with the addition of a relatively simple transistor amplifier circuit. With such a modification you could plug the CoCo into the composite video input on a more modern TV and get an improved (though still far from perfect) picture. But if you do this, you'll also need to do something similar for the CoCo's audio signal if you want to hear it, since the audio is ordinarily modulated into the RF signal along with the video.

The CoCo originally came with a long, black, thin coaxial cable with RCA plugs on either end, and a little metal box that contained an inductor and a switch. One end of the cable plugs into the TV output on the rear CoCo, and the other end plugs into a connector on the box. The box also had an RF connector to hook up a coaxial cable coming from your TV antenna, and some short wires that would attach to the antenna connector on your TV. The switch could then be used to select the antenna, for TV viewing, or the CoCo. If you have picked up a secondhand CoCo from a thrift shop, it is entirely possible that the cable and/or the antenna switch box didn't come along with it. You should be able to use an audio/video cable with RCA plugs for the RF, and the TV game switches may still be available at Radio Shack and elsewhere. The same type of switch has been used with video game consoles that are intended to connect to the TV.