From: "W. Ivey" Newsgroups: alt.folklore.computers Subject: Looking for info on relay logic Lines: 33 X-Priority: 3 X-MSMail-Priority: Normal X-Newsreader: Microsoft Outlook Express 5.50.4133.2400 X-MimeOLE: Produced By Microsoft MimeOLE V5.50.4133.2400 Message-ID: Date: Wed, 27 Sep 2000 04:36:04 GMT NNTP-Posting-Host: 208.194.204.205 X-Complaints-To: abuse@flash.net X-Trace: news.flash.net 970029364 208.194.204.205 (Tue, 26 Sep 2000 23:36:04 CDT) NNTP-Posting-Date: Tue, 26 Sep 2000 23:36:04 CDT Organization: FlashNet Communications, http://www.flash.net Path: chonsp.franklin.ch!pfaff.ethz.ch!news-zh.switch.ch!newsfeed-zh.ip-plus.net!news.ip-plus.net!news.tesion.net!news.belwue.de!news-stu1.dfn.de!news-koe1.dfn.de!RRZ.Uni-Koeln.DE!news.netcologne.de!newsfeed.germany.net!newscore.gigabell.net!isdnet!howland.erols.net!nntp.flash.net!news.flash.net!not-for-mail Xref: chonsp.franklin.ch alt.folklore.computers:64886 First, don't laugh... I was browsing ebay the other day and saw an ad for several hundred relays - cheap. I started thinking about what I could use several hundred cheap relays for. Then I started thinking about the good old days when you could _hear_ a CPU at work. Ah, the clacking of contacts! (OK, I'm not that old, actually.) So I started drawing assorted logic functions based on SPDT, DPDT and 4PDT relays: RS latch, D F/F, 1 of 4 and 1 of 8 decoders, and a 4-bit full adder. I realized that designing with relays and designing with IC logic gates were totally different beasts in a lot of ways. So, back to the subject. Does anyone know a good site with some design information about the old relay-logic based computers? (I've found some very interesting sites - one that went into the history of Zeus's mechanical/electro-mechanical machines - but none with any basic design info.) I know relay logic, if not computers, was in use at least as far back as the opening of the Panama Canal because it's controlled by a GE relay "computer." There ought to be something on the net by now, right? Thanks for any leads. -Wm ###### From: Dennis Ritchie Newsgroups: alt.folklore.computers Subject: Re: Looking for info on relay logic Date: Wed, 27 Sep 2000 06:31:04 +0000 Organization: Bell Labs / Lucent Technologies Lines: 36 Message-ID: <39D19428.69A510FE@bell-labs.com> References: NNTP-Posting-Host: trux.cs.bell-labs.com Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit X-Mailer: Mozilla 4.61 [en] (WinNT; U) X-Accept-Language: en Path: chonsp.franklin.ch!pfaff.ethz.ch!news-zh.switch.ch!newsfeed-zh.ip-plus.net!news.ip-plus.net!news.tesion.net!news.belwue.de!informatik.tu-muenchen.de!news.informatik.uni-muenchen.de!uni-erlangen.de!newsfeeds.belnet.be!news.belnet.be!news-spur1.maxwell.syr.edu!news.maxwell.syr.edu!wn4feed!worldnet.att.net!207.24.196.41!nntphub.cb.lucent.com!news Xref: chonsp.franklin.ch alt.folklore.computers:64873 "W. Ivey" wrote: .... > So, back to the subject. Does anyone know a good > site with some design information about the old > relay-logic based computers? (I've found some very > interesting sites - one that went into the history > of Zeus's mechanical/electro-mechanical machines - > but none with any basic design info.) I know relay > logic, if not computers, was in use at least as > far back as the opening of the Panama Canal because > it's controlled by a GE relay "computer." There ought > to be something on the net by now, right? > > Thanks for any leads. -Wm You could go to www.abebooks.com and find a seller of Keister, Ritchie, Washburn: The Design of Switching Circuits for example the one at http://dogbert.abebooks.com/abe/BookDetails?bi=79252103 which happens to be listed first (at $20); there are several others listed for sale at $10. Not mainly about computers, but a lot about system design for relays, and there is a chapter on Circuits for Calculating. Problem for Ch 21: An adding circuit is to be designed to determine the sum of two five-digit binary numbers.... (This can be done with ten relays). No financial interest, since the second author's estate was settled a while ago, but the name is not by coincidence. And I'm not selling my copy, signed by all three authors. Dennis ###### Newsgroups: alt.folklore.computers Subject: Re: Looking for info on relay logic References: <39D19428.69A510FE@bell-labs.com> Organization: None X-Newsreader: trn 4.0-test72 (19 April 1999) From: kragen@dnaco.net (Kragen Sitaker) Lines: 24 Message-ID: X-Abuse-Info: Please be sure to forward a copy of ALL headers X-Abuse-Info: Otherwise we will be unable to process your complaint properly X-Complaints-To: support@usenetserver.com NNTP-Posting-Date: Wed, 27 Sep 2000 05:07:34 EDT Date: Wed, 27 Sep 2000 09:07:34 GMT Path: chonsp.franklin.ch!pfaff.ethz.ch!news-zh.switch.ch!news-ge.switch.ch!news-fra1.dfn.de!news0.de.colt.net!colt.net!newspeer.clara.net!news.clara.net!newsfeed.icl.net!newsfeed.skycache.com!Cidera!cyclone2.usenetserver.com!news-out.usenetserver.com!cyclone1.usenetserver.com!news-east.usenetserver.com.POSTED!not-for-mail Xref: chonsp.franklin.ch alt.folklore.computers:64868 In article <39D19428.69A510FE@bell-labs.com>, Dennis Ritchie wrote: >"W. Ivey" wrote: > .... >> So, back to the subject. Does anyone know a good >> site with some design information about the old >> relay-logic based computers? > >You could go to www.abebooks.com and find a seller of > Keister, Ritchie, Washburn: The Design of Switching Circuits > . . . >Not mainly about computers, but a lot about system design >for relays, and there is a chapter on Circuits for Calculating. This book gave me many hours of pleasant contemplation during my childhood. I found relays and gas tubes much more comprehensible than transistors and resistors. :) I'm not selling my copy either :) -- Kragen Sitaker Perilous to all of us are the devices of an art deeper than we ourselves possess. -- Gandalf the Grey [J.R.R. Tolkien, "Lord of the Rings"] ###### Message-ID: <39D26B5A.66F6@indyx.net> From: freddy1X Reply-To: freddy1X Organization: IndyNet X-Mailer: Mozilla 3.04C-IndyNet (Win16; I) MIME-Version: 1.0 Newsgroups: alt.folklore.computers Subject: Re: Looking for info on relay logic References: Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Lines: 51 Date: Wed, 27 Sep 2000 17:49:14 -0400 NNTP-Posting-Host: 209.183.93.59 X-Complaints-To: abuse@onemain.com X-Trace: nntp2.onemain.com 970095192 209.183.93.59 (Wed, 27 Sep 2000 18:53:12 EDT) NNTP-Posting-Date: Wed, 27 Sep 2000 18:53:12 EDT Path: chonsp.franklin.ch!pfaff.ethz.ch!news-zh.switch.ch!newsfeed-zh.ip-plus.net!news.ip-plus.net!news.tesion.net!news.belwue.de!news-stu1.dfn.de!news-koe1.dfn.de!RRZ.Uni-Koeln.DE!news.netcologne.de!newsfeed01.sul.t-online.de!t-online.de!newspeer.clara.net!news.clara.net!feed2.onemain.com!feed1.onemain.com!nntp2.onemain.com.POSTED!not-for-mail Xref: chonsp.franklin.ch alt.folklore.computers:65056 W. Ivey wrote: > > First, don't laugh... > > I was browsing ebay the other day and saw an ad for > several hundred relays - cheap. I started thinking > about what I could use several hundred cheap relays > for. > > Then I started thinking about the good old days when > you could _hear_ a CPU at work. Ah, the clacking of > contacts! (OK, I'm not that old, actually.) > > So, back to the subject. Does anyone know a good > site with some design information about the old > relay-logic based computers? (I've found some very > interesting sites - one that went into the history > of Zeus's mechanical/electro-mechanical machines - > but none with any basic design info.) I know relay > logic, if not computers, was in use at least as > far back as the opening of the Panama Canal because > it's controlled by a GE relay "computer." There ought > to be something on the net by now, right? > > Thanks for any leads. -Wm You might also check out references for pre-1980 pinball machines. We have one of the classics at home, and I find it amazing at what they were able to accomplish with about 2 dozen relays, a bunch of counters and target switches( essentially worked as latches ). Nothing compares to the hum of the coils, the clicking of the relays, and the sparking contacts. We were fortunate that it came complete with the schematics, and even with them, it was an interesting task to isolate a malfunction by the logic flow, find the correct set of contacts, and restore operation. Usually contact pitting. Lots of wires, exposed contacts, and warm parts. Most of it operated on 24Vac, but they had 120 volts in a few spots for laughs. Overall, educational, and entertaining, just enough functions for a "real world" example. -- for external use only /\>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>\/ /\ I may be demented \/ /\ but I'm not crazy! \/ /\<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<\/ * SPAyM trap: there is no X in my address * || attatch FLAME here || \/ \/ X ###### From: "Geoffrey G. Rochat" Newsgroups: alt.folklore.computers Subject: Re: Looking for info on relay logic Date: Wed, 27 Sep 2000 23:51:10 -0400 Organization: Kersur Technologies Lines: 58 Message-ID: <8quel9$arv$1@news.kersur.net> References: NNTP-Posting-Host: 10-069.024.popsite.net X-Trace: news.kersur.net 970112489 11135 216.126.162.69 (28 Sep 2000 03:41:28 GMT) X-Complaints-To: usenet@kersur.net NNTP-Posting-Date: 28 Sep 2000 03:41:28 GMT X-Newsreader: Microsoft Outlook Express 4.72.3110.1 X-MimeOLE: Produced By Microsoft MimeOLE V4.72.3110.3 Path: chonsp.franklin.ch!pfaff.ethz.ch!news-zh.switch.ch!news-ge.switch.ch!bignews.mediaways.net!xfer10.netnews.com!netnews.com!hermes.visi.com!news-out.visi.com!uunet!ffx.uu.net!news.kersur.net!not-for-mail Xref: chonsp.franklin.ch alt.folklore.computers:65089 W. Ivey wrote in message ... >First, don't laugh... > >I was browsing ebay the other day and saw an ad for >several hundred relays - cheap. I started thinking >about what I could use several hundred cheap relays >for. > >Then I started thinking about the good old days when >you could _hear_ a CPU at work. Ah, the clacking of >contacts! (OK, I'm not that old, actually.) > >So I started drawing assorted logic functions based >on SPDT, DPDT and 4PDT relays: RS latch, D F/F, 1 of >4 and 1 of 8 decoders, and a 4-bit full adder. I >realized that designing with relays and designing >with IC logic gates were totally different beasts >in a lot of ways. > >So, back to the subject. Does anyone know a good >site with some design information about the old >relay-logic based computers? (I've found some very >interesting sites - one that went into the history >of Zeus's mechanical/electro-mechanical machines - >but none with any basic design info.) I know relay >logic, if not computers, was in use at least as >far back as the opening of the Panama Canal because >it's controlled by a GE relay "computer." There ought >to be something on the net by now, right? > >Thanks for any leads. -Wm Sections 5-5 "Relay Networks" and 5-6 "Analysis and Synthesis of Contact Networks" in "Switching and Finite Automata Theory" by Zvi Kohavi (McGraw-Hill, 1978, ISBN 0-07-035310-7) has much of what you want, and should be widely available from used book sources like www.powells.com or www.alibris.com as the book was a commonly-used undergrad and grad text in logic design courses circa 1980. You're quite right about relay logic being a "whole n'other thing" than gate logic. For one thing, unlike gates relays are bidirectional, so you can get signals travelling in both directions. When this happens where you don't want it, it's called a sneak path. But where you *do* want it you can get all sorts of interesting simplifications. Relay logic is, of course, obsolete these days for most applications (other than enthusiasts out to experiment and to challenge their brain cells with interesting new stuff), but the bidirectional nature of relays may be found in more modern garb in the transmission gates available in CMOS, particularly chips such as the CD4066. In particular, take a look at the logic diagrams for things like D flip-flops in the CD4000-series, and you'll see they're full of transmission gate. > > > ###### From: "Philo" Newsgroups: alt.folklore.computers References: Subject: Re: Looking for info on relay logic Date: Thu, 28 Sep 2000 08:41:21 -0500 X-Priority: 3 X-MSMail-Priority: Normal X-Newsreader: Microsoft Outlook Express 5.00.2314.1300 X-MimeOLE: Produced By Microsoft MimeOLE V5.00.2314.1300 Lines: 28 Message-ID: <39d34acb$0$146$736b3e2@news2.twtelecom.net> NNTP-Posting-Host: 207.250.192.142 X-Trace: 970148556 news2.twtelecom.net 146 207.250.192.142 Path: chonsp.franklin.ch!pfaff.ethz.ch!news-zh.switch.ch!newsfeed-zh.ip-plus.net!news.ip-plus.net!news.tesion.net!news.belwue.de!informatik.tu-muenchen.de!news.informatik.uni-muenchen.de!uni-erlangen.de!newsfeed.germany.net!fr.clara.net!small.fr.clara.net!xfer10.netnews.com!netnews.com!upp1.onvoy!onvoy.com!newsengine.sol.net!newstest.sol.net!news.execpc.com!newspeer.sol.net!nntp.twtelecom.net!news.twtelecom.net!news.twtelecom.net!not-for-mail Xref: chonsp.franklin.ch alt.folklore.computers:65027 i'm sure not laughing...because when i was in college... i actually did some relay logic designs. vacuum tubes were still in use... and we weren't sure if we could really trust those transistors... however relay logic is really no different from any other logic... you just setup your truth table and go. yes it's slow and cumbersome...but there are some uses for it... i repair industrial equipment for a living and occasionally do some design work. well, for one project where i had to really low dollar the bid...i decided to use up boxes of relays that one idiot in my department purchased for a project that never went through... since the parts were already written off... i designed a nice relay logic device to upgrade some industrial battery chargers from manual to automatic start. i got the order and used up all the relays... over the last 15 years there have been a few major power surges which did quite a bit of damage...but not one of the relay logic devices was ever affected... not only that... i have the entire account pretty well sewed up as none of my competitiors can figure out the rats nest i have created!!! Philo ###### From: "W. Ivey" Newsgroups: alt.folklore.computers References: <39D19428.69A510FE@bell-labs.com> Subject: Re: Looking for info on relay logic Lines: 14 X-Priority: 3 X-MSMail-Priority: Normal X-Newsreader: Microsoft Outlook Express 5.50.4133.2400 X-MimeOLE: Produced By Microsoft MimeOLE V5.50.4133.2400 Message-ID: <4qQA5.514$Sa.24345@news.flash.net> Date: Thu, 28 Sep 2000 23:23:44 GMT NNTP-Posting-Host: 208.194.203.25 X-Complaints-To: abuse@flash.net X-Trace: news.flash.net 970183424 208.194.203.25 (Thu, 28 Sep 2000 18:23:44 CDT) NNTP-Posting-Date: Thu, 28 Sep 2000 18:23:44 CDT Organization: FlashNet Communications, http://www.flash.net Path: chonsp.franklin.ch!pfaff.ethz.ch!news-zh.switch.ch!newsfeed-zh.ip-plus.net!news.ip-plus.net!news.tesion.net!news.belwue.de!informatik.tu-muenchen.de!news.csl-gmbh.net!blackbush.xlink.net!renate.komtel.net!news.tele.dk!209.50.235.254!europa.netcrusader.net!205.252.116.205!howland.erols.net!nntp.flash.net!news.flash.net!not-for-mail Xref: chonsp.franklin.ch alt.folklore.computers:64987 "Dennis Ritchie" wrote in message news:39D19428.69A510FE@bell-labs.com... > > > You could go to www.abebooks.com and find a seller of > Keister, Ritchie, Washburn: The Design of Switching Circuits > for example the one at > http://dogbert.abebooks.com/abe/BookDetails?bi=79252103 > which happens to be listed first (at $20); there are > several others listed for sale at $10. Thanks, I'll have to look into that. -Wm ###### From: "W. Ivey" Newsgroups: alt.folklore.computers References: <39D19428.69A510FE@bell-labs.com> Subject: Re: Looking for info on relay logic Lines: 14 X-Priority: 3 X-MSMail-Priority: Normal X-Newsreader: Microsoft Outlook Express 5.50.4133.2400 X-MimeOLE: Produced By Microsoft MimeOLE V5.50.4133.2400 Message-ID: <4qQA5.514$Sa.24345@news.flash.net> Date: Thu, 28 Sep 2000 23:23:44 GMT NNTP-Posting-Host: 208.194.203.25 X-Complaints-To: abuse@flash.net X-Trace: news.flash.net 970183424 208.194.203.25 (Thu, 28 Sep 2000 18:23:44 CDT) NNTP-Posting-Date: Thu, 28 Sep 2000 18:23:44 CDT Organization: FlashNet Communications, http://www.flash.net Path: chonsp.franklin.ch!pfaff.ethz.ch!news-zh.switch.ch!newsfeed-zh.ip-plus.net!news.ip-plus.net!news.tesion.net!news.belwue.de!informatik.tu-muenchen.de!news.csl-gmbh.net!blackbush.xlink.net!renate.komtel.net!news.tele.dk!209.50.235.254!europa.netcrusader.net!205.252.116.205!howland.erols.net!nntp.flash.net!news.flash.net!not-for-mail Xref: chonsp.franklin.ch alt.folklore.computers:65082 "Dennis Ritchie" wrote in message news:39D19428.69A510FE@bell-labs.com... > > > You could go to www.abebooks.com and find a seller of > Keister, Ritchie, Washburn: The Design of Switching Circuits > for example the one at > http://dogbert.abebooks.com/abe/BookDetails?bi=79252103 > which happens to be listed first (at $20); there are > several others listed for sale at $10. Thanks, I'll have to look into that. -Wm ###### From: "W. Ivey" Newsgroups: alt.folklore.computers References: <8quel9$arv$1@news.kersur.net> Subject: Re: Looking for info on relay logic Lines: 16 X-Priority: 3 X-MSMail-Priority: Normal X-Newsreader: Microsoft Outlook Express 5.50.4133.2400 X-MimeOLE: Produced By Microsoft MimeOLE V5.50.4133.2400 Message-ID: Date: Thu, 28 Sep 2000 23:26:24 GMT NNTP-Posting-Host: 208.194.203.25 X-Complaints-To: abuse@flash.net X-Trace: news.flash.net 970183584 208.194.203.25 (Thu, 28 Sep 2000 18:26:24 CDT) NNTP-Posting-Date: Thu, 28 Sep 2000 18:26:24 CDT Organization: FlashNet Communications, http://www.flash.net Path: chonsp.franklin.ch!pfaff.ethz.ch!news-zh.switch.ch!newsfeed-zh.ip-plus.net!news.ip-plus.net!News.Amsterdam.UnisourceCS!skynet.be!howland.erols.net!nntp.flash.net!news.flash.net!not-for-mail Xref: chonsp.franklin.ch alt.folklore.computers:65085 "Geoffrey G. Rochat" wrote in message news:8quel9$arv$1@news.kersur.net... > [...] > logic being a "whole n'other thing" than gate logic. For one thing, > unlike gates relays are bidirectional, so you can get signals travelling > in both directions. When this happens where you don't want it, it's > called a sneak path. But where you *do* want it you can get all sorts > of interesting simplifications. Yeah, I noticed that :-) It became obvious that if I "adulterated" my component selection with a few well placed diodes a lot of things would be simplified. -Wm ###### X-Posting-Agent: Hamster/1.3.21.100 From: Nick Spalding Newsgroups: alt.folklore.computers Subject: Re: Looking for info on relay logic Reply-To: spalding@iol.ie Message-ID: References: <8quel9$arv$1@news.kersur.net> X-Newsreader: Forte Agent 1.8/32.548 MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Lines: 10 Date: Fri, 29 Sep 2000 10:29:47 GMT NNTP-Posting-Host: 193.203.147.16 X-Complaints-To: abuse@iol.ie X-Trace: news.iol.ie 970223387 193.203.147.16 (Fri, 29 Sep 2000 11:29:47 BST) NNTP-Posting-Date: Fri, 29 Sep 2000 11:29:47 BST Organization: Ireland On-Line Customer Path: chonsp.franklin.ch!pfaff.ethz.ch!news-zh.switch.ch!news-ge.switch.ch!news-fra1.dfn.de!news-koe1.dfn.de!RRZ.Uni-Koeln.DE!news.netcologne.de!news-spur1.maxwell.syr.edu!news.maxwell.syr.edu!newsfeed.esat.net!news.iol.ie!not-for-mail Xref: chonsp.franklin.ch alt.folklore.computers:65053 W. Ivey wrote, in : > Yeah, I noticed that :-) It became obvious that if I "adulterated" > my component selection with a few well placed diodes a lot of things > would be simplified. -Wm You would have a precedent. Diodes with plug ends were one of the things one had available to wire up panels for IBM tabs, collators etc. -- Nick Spalding ###### From: jcmorris@jmorris-pc.MITRE.ORG (Joe Morris) Newsgroups: alt.folklore.computers Subject: Re: Looking for info on relay logic Date: 29 Sep 2000 14:39:09 GMT Organization: The MITRE Corporation Lines: 13 Message-ID: <8r29id$kq8$1@top.mitre.org> References: <39d34acb$0$146$736b3e2@news2.twtelecom.net> NNTP-Posting-Host: jmorris-pc.mitre.org X-Trace: top.mitre.org 970238349 21320 128.29.251.13 (29 Sep 2000 14:39:09 GMT) X-Complaints-To: usenet@news.mitre.org NNTP-Posting-Date: 29 Sep 2000 14:39:09 GMT X-Newsreader: NN version 6.5.0 (NOV) Path: chonsp.franklin.ch!pfaff.ethz.ch!news-zh.switch.ch!newsfeed-zh.ip-plus.net!news.ip-plus.net!news.tesion.net!news.belwue.de!fu-berlin.de!arclight.uoregon.edu!news.tufts.edu!blanket.mitre.org!news.mitre.org!jmorris-pc.MITRE.ORG!jcmorris Xref: chonsp.franklin.ch alt.folklore.computers:64946 "Philo" writes: >i designed a nice relay logic device to upgrade some industrial battery >chargers from manual to automatic start. >i got the order and used up all the relays... >over the last 15 years there have been a few major power surges which did >quite a bit of damage...but not one of the relay logic devices was ever >affected... It's occasionally been pointed out that for some high-current applications you want to use solid-state devices -- as in "solid copper". Joe Morris ###### Newsgroups: alt.folklore.computers References: <1c74tsc8so6e6dcqq710l4rk5pjvn4l8b1@4ax.com> From: jata@aepiax.net (Julian Thomas) Subject: Re: Looking for info on relay logic Message-ID: <39d7eb7f$2$wg$mr2ice@news.epix.net> X-Newsreader: MR/2 Internet Cruiser Edition for OS/2 v2.2a/20 Lines: 29 Date: Mon, 02 Oct 2000 01:57:22 GMT NNTP-Posting-Host: 199.224.125.89 X-Complaints-To: abuse@epix.net X-Trace: news1.epix.net 970451842 199.224.125.89 (Sun, 01 Oct 2000 21:57:22 EDT) NNTP-Posting-Date: Sun, 01 Oct 2000 21:57:22 EDT Path: chonsp.franklin.ch!pfaff.ethz.ch!news-zh.switch.ch!machtgarnix.switch.ch!news-ge.switch.ch!isdnet!newspump.monmouth.com!newspeer.monmouth.com!news-xfer.epix.net!news1.epix.net!not-for-mail Xref: chonsp.franklin.ch alt.folklore.computers:65206 In <1c74tsc8so6e6dcqq710l4rk5pjvn4l8b1@4ax.com>, on 09/27/00 at 04:22 PM, David Razler said: >It's easier, for the most part, assuming all the relays use the same >voltage to the coils and you know which ones latch and which don't. >But don't expect any great speed. In High School, we took a bunch of >(H/P??) "Logic Lab trainers", briefcase-size devices with power supplies, >four relays, four switches, four lightbulbs and plugs to wire them all up >in any pattern you wished When I was a grad school teaching assistant at Harvard (in Aiken's Comp Lab), we had a relay plugboard (relays, pushbuttons, toggle switches, lights)- and one of the courses included an exercise to wire up some function or other on the board. When it was all done, I asked the students if they knew the most common relay circuit - few of them did. I proceeded to wire up a simple buzzer circuit. -- Julian Thomas: jt . epix @ net http://home.epix.net/~jt remove letter a for email (or switch . and @) In the beautiful Finger Lakes Wine Country of New York State! Boardmember of POSSI.org - Phoenix OS/2 Society, Inc http://www.possi.org -- -- Old age and treachery will always overcome youth and skill. ###### From: "William" Newsgroups: alt.folklore.computers References: <1c74tsc8so6e6dcqq710l4rk5pjvn4l8b1@4ax.com> <39d7eb7f$2$wg$mr2ice@news.epix.net> Subject: Re: Looking for info on relay logic Lines: 15 X-Priority: 3 X-MSMail-Priority: Normal X-Newsreader: Microsoft Outlook Express 5.50.4133.2400 X-MimeOLE: Produced By Microsoft MimeOLE V5.50.4133.2400 Message-ID: Date: Mon, 02 Oct 2000 14:30:57 GMT NNTP-Posting-Host: 216.40.83.18 X-Complaints-To: abuse@flash.net X-Trace: news.flash.net 970497057 216.40.83.18 (Mon, 02 Oct 2000 09:30:57 CDT) NNTP-Posting-Date: Mon, 02 Oct 2000 09:30:57 CDT Organization: FlashNet Communications, http://www.flash.net Path: chonsp.franklin.ch!pfaff.ethz.ch!news-zh.switch.ch!newsfeed-zh.ip-plus.net!news.ip-plus.net!news.tesion.net!news.belwue.de!fu-berlin.de!nntp.flash.net!news.flash.net!not-for-mail Xref: chonsp.franklin.ch alt.folklore.computers:65187 "Julian Thomas" wrote in message news:39d7eb7f$2$wg$mr2ice@news.epix.net... > In <1c74tsc8so6e6dcqq710l4rk5pjvn4l8b1@4ax.com>, on 09/27/00 > at 04:22 PM, David Razler said: > > When I was a grad school teaching assistant at Harvard (in Aiken's Comp > Lab), we had a relay plugboard (relays, pushbuttons, toggle switches, > lights)- and one of the courses included an exercise to wire up some > function or other on the board. When it was all done, I asked the > students if they knew the most common relay circuit - few of them did. I > proceeded to wire up a simple buzzer circuit. Cool, an astable multivibrator with built in audio transducer :-) -Wm