SPACEWAR! Switch Boxes for a PDP-12

Brent Hilpert bhilpert at
Sun Sep 23 12:58:19 CDT 2018

On 2018-Sep-23, at 7:46 AM, Michael Thompson via cctech wrote:

> Visitors to the RICM like to play SPACEWAR! in the PDP-12. Unfortunately
> using the console switches is uncomfortable, not intuitive, and is tough on
> the switches. We would like to recreate the switch boxes used on the PDP-1
> to make playing a better experience.
> We modified the source
> <>
> from D.E. WREGE
> <;fn=images/jby/jbyos8.tu56;to=ascii;blk=510,131,0;plain=1>
> to use the LINC SXL instruction to read the PDP-12 GPIO signals, and
> prototyped two switch boxes using recycled toggle switches. This works
> great, so now we need to make better switch boxes.
> This CHM article shows what we want to recreate.
> <>
> This article shows a sketch of the switch boxes.
> <>
> A generous donor made these boxes for us.
> <>
> The lever switches are turning our to be difficult to find at a reasonable
> price. We found some NOS SwitchCraft lever switches that looked like the
> sketch and the PDP-1 pictures and were a reasonable price, but our order
> was rejected because they only had one in stock. eBay has Mossman and
> SwitchCraft, but they are either very expensive (more than $50 each), or
> they only have one available.
> The switches that we are looking for need to be SPDT, three-position,
> non-locking, center off. (If the switches have more than one pole we can
> remove the extra poles to keep the operational force low.) Before we cave
> in and buy some modern C&K toggle switches, does anyone have a source for
> Mossman or SwitchCraft switches at a reasonable price?

You haven't provided much detail about what limits you're willing to entertain in style of switch.

There are a wide variety of lever switches available.
There are leaf-contact switches that mount with two screws and a slot for the lever,
leaf-contact with a throated actuator that mount in a 1/2 inch hole (much easier to mount than making a narrow slot),
wafer switches with the two-screw/slot mount, etc.
Slot-styles may have the lever plane made from stamped/sheet metal with a slide on knob vs. made from thick ~3/16-1/8 inch metal with a thread-on knob.
The latter were very robust and the type typically found in telephone switchboards, although there were also some cheaper japanese makes.

Do you want period-correct even if not the exact manuf/type originally used, or when you mention C&K are you referring to modern mini-toggles as acceptable?

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