Front panel switches - what did they do?

Marc Howard cramcram at
Tue May 24 12:13:11 CDT 2016

Those aren't LED's on the Apollo display.  They are EL's (Electro
Luminescent displays).  Each segment of each digit was controlled by a
relay.  They astronauts eventually got use to the tinkling sound of the

In fact the entire console panel of the command module was a giant EL,
covered mostly in gray paint except where switch legends were needed.  ELs
were highly reliable and dim-able. Unfortunately they required a relatively
high voltage (22 volts or so) which is why relays were needed to control
the display segments on the computer readouts.

I'm surprised no one has mentioned the control panel of the IBM 360/91:


On Tue, May 24, 2016 at 9:54 AM, Swift Griggs <swiftgriggs at> wrote:

> On Tue, 24 May 2016, Charles Anthony wrote:
> > Honeywell 6180 display panels:
> >
> Holy rocker switch, Batman! Is that all for one machine? That looks like a
> man-machine interface to run a nuclear power plant or something. FOUR
> panels. The black panel looks uber-cool. That definitely looks like
> something from a 60's or 70's James bond film. There needs to be a villain
> about ready to launch a missile standing next to one.
> Oh and here is a replica of an Apollo launch computer with a component LED
> display like I was mentioning:
> ... probably too expensive to embed in a computer system, but still hard
> to beat for geek aesthetics.
> -Swift

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