"Consequently levels of +5 and 0 volts will, in most normal cases, work, although they are out of specification"
Yes, they work by accident. Until they don't. 73, Cliff K3LL -----Original Message----- From: Elecraft [mailto:[email protected]] On Behalf Of David Woolley Sent: Friday, January 22, 2016 6:45 AM To: [email protected] Subject: Re: [Elecraft] Long RS232 Runs - RS422 The +/- 3 volts levels are requirements on the driver, not the receiver. In practice, receivers have quite a small hysteresis, and the threshold points are set to meet the requirements of a type 1 interface as defined in section 7 of ITU-T V.28. Whilst the specified purpose of this is that a powered down or open circuit condition should result in defined states for, particularly control signals (off), in practice it means that real world receivers will also handle high speed signals which are strictly positive. Consequently levels of +5 and 0 volts will, in most normal cases, work, although they are out of specification. ITU-T V.28 is generally aligned with the electrical characteristics of EIA232, but has the advantage that the document is available for free download. -- David Woolley Owner K2 06123 On 21/01/16 20:03, Cliff Frescura wrote: > RS-232 use +3 to +15VDC and -3 to -15VDC for signaling levels, thus -5 > and +5 will work too, but *not* 0VDC and +5VDC > ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[email protected] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [email protected] ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[email protected] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [email protected]
