Article 5628 of alt.sys.pdp10: Path: news3.best.com!news2.best.com!feed1.news.rcn.net!rcn!not-for-mail From: Sheila&bob/Herbal Gypsy and the Tinker Newsgroups: alt.folklore.computers,alt.sys.pdp8,alt.sys.pdp11,alt.sys.pdp10 Subject: Re: ASR 33 Typing Element Date: Sun, 29 Aug 1999 11:08:40 -0400 Lines: 35 Message-ID: <37C94CF8.3F5DC717@erols.com> References: <935832140.772977@estelle.paradise.net.nz> <935924429.273399@estelle.paradise.net.nz> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit X-Trace: zCknCAsw4kyTkPHK9qvDfnghWj29gvxodGl9ZW/4UN8= X-Complaints-To: abuse@rcn.com NNTP-Posting-Date: 29 Aug 1999 15:06:31 GMT X-Accept-Language: en X-Mailer: Mozilla 4.61 [en] (WinNT; U) Xref: news3.best.com alt.folklore.computers:138438 alt.sys.pdp8:3120 alt.sys.pdp11:5569 alt.sys.pdp10:5628 Ric Werme wrote: > > don@news.daedalus.co.nz (Don Stokes) writes: > > >Terry Kennedy writes: > > >> Expecting to power anything off a MAX232's -V is pretty much a forlorn > >>hope. While it does meet the RS-232 specs (at something like -4.2V) > >>there isn't enough "oomph" to do anything more than drive a RS-232 > >>receiver. > > I thought RS232 specs call for between 5 and 12 volts, for both > positive and negative signals. (Or is it 3 to 12?) The RS232 Spec (note that there is no letter after the number!) to be able to receive voltage swings of -/+ 25 volts on hte high side and detect =/-3V so you had a 6 volt band to copensate for noise. The spec also said put out upto +/-12V on the high side. that was great in transistor and DCD driver times but with ICs, got to be a bit much and then we had this little problem with slew rate....as you go up in speed.... The voltages changed a bit by the tiem we got to RS232C, but the receive spec was still the same, even tho most folks were running max out put based on +/-12 volt rails. DEC Comm 11 did a study of cable type, distance and speed. High capacitance cable limited speed and distance. RS423 helped solve a whole raft of problems.....including incompat. with MIL-STD 188C... bob > -- > Ric Werme | http://people.ne.mediaone.net/werme > werme@nospam.mediaone.net | http://www.cyberportal.net/werme > ^^^^^^^ delete