Indicator tubes for transistor logic machines.

Yes, the modules are color-coded. The "F/F" modules with the indicator tubes (6977's) are silver, with a contrasting black stripe around the slot where the logic indicator tube shines through. There are also some reddish 'D' modules, and one or two other types. What's sort of interesting is that the 'F/F' module and the 'D' module both use exactly the same artwork, but have very different drilling patterns. The modules don't look very similar, but each type has 'extra' etch and pad areas that are used on the other module types. Someone really thought this through carefully. These logic modules are an interesting sort of 'logic family', like RTL or TTL that's not been shrunken down onto chips. Oh yes, I just got the logic display tubes to fire up on the bench. The grids glow! They are coated with phosphor. The anode is totally dark, and a tiny voltage on the grid switches the phosphors on and off. A vacuum tube triode designed for 'transistorized computers'! Very cool. ----- Original Message ----- From: "William Donzelli" <wdonzelli at gmail.com> To: "General Discussion: On-Topic and Off-Topic Posts" <cctalk at classiccmp.org> Sent: Sunday, October 28, 2007 2:43 PM Subject: Re: Indicator tubes for transistor logic machines.