From: "Cini, Richard" <RCini(a)congressfinancial.com> OK, this might sound like a stupid question, but being somewhat ignorant of RTL logic in comparison to TTL and other designs, what, if anything, can be substituted for RTL logic chips? For example, if I wanted to build one of Don's devices and I wasn't concerned with using "vintage" chips, could I do it "plug-and-play" using current TTL? Rich -----Original Message----- From: cctalk-bounces(a)classiccmp.org [mailto:cctalk-bounces@classiccmp.org]On Behalf Of Michael Holley Sent: Friday, January 07, 2005 12:08 AM To: cctalk(a)classiccmp.org Subject: RTL Logic I have acquired some Don Lancaster designs that use RTL logic and I am looking for spare parts. The MC789 hex inverter is used in all of them and I have 2 chips. Does anyone have a reasonable source for the MC789, I can get all I want for $20 a chip. I also have 2 MC799 buffers that are use in the Microlab. I have found two each of these (MC725, MC778, MC785, MC792, MC853, MC855) that I will part with. SWTPC Digital Logic Microlab http://www.swtpc.com/mholley/PopularElectronics/Apr1970/PE_Apr1970.htm Early SWTPC keyboard http://www.swtpc.com/mholley/PopularElectronics/Apr1974/PE_Apr1974.htm I think that Don Lancaster's TIC TAC TOE machine from 1971 is a very clever design. It uses 5 ICs and 60 diodes to play the game. I may build one. http://www.swtpc.com/mholley/RadioElectronics/Dec1971/RE_Dec1971.htm Michael Holley www.swtpc.com/mholley