Notes
The pause button Coleco never built.
When the ColecoVision launched in 1982, it shipped without a system-wide pause function. Some game cartridges built pause into their own code — a * or # key press on the controller keypad — but many didn't. If the phone rang mid-game, or the dog needed out, or dinner was ready and you weren't done with the level, your only options were to die on purpose or leave the console running.
Video Additions, Inc. saw the gap and built the Add-A-Halt.
Flip the switch to HALT and the game freezes exactly where it is. Flip it back to RUN and play continues from the same frame. Universal pause, hardware-level, works on every cartridge — because it doesn't rely on the cartridge to cooperate.
How it works. The ColecoVision runs on a Zilog Z80A processor at 3.58 MHz. The Z80 has a well-known behavior — when its clock is stopped or its WAIT line is held active, the CPU preserves its complete internal state. Registers freeze. The program counter stops. Video refresh from the TMS9928A pauses at whatever screen it was drawing. Everything holds. When the control line is released, the CPU resumes exactly where it left off, oblivious to the pause.
The Add-A-Halt exploits this by driving the appropriate control line on the expansion connector through the toggle switch. No processor modification. No cartridge modification. No software involvement of any kind. Just a switch, an LED, some wire, and knowledge of the Z80's architecture.
One quirk that's endearing. Because the halt happens at the CPU clock level and doesn't involve the sound chip's own state, if the Add-A-Halt is thrown mid-note, the SN76489 audio chip continues outputting whatever tone it was generating at that instant. The picture freezes silently... except for one held note, buzzing endlessly until the switch flips back to RUN. Reports from the community confirm this behavior on every game tested.
How rare is it today? Very. Despite the documented period marketing, surviving units almost never surface on the collector market, and Video Additions, Inc. left behind no other identifiable product line.
If you own an Add-A-Halt — or, better yet, have an ad in its original magazine or newsletter context — the ColecoVision preservation community would love to see it. Documenting the publication and issue date would fill in one of the last unknowns about this obscure but genuinely inventive third-party accessory.
