[time-nuts] Z3805 utility, Was: AW: (no subject)

Sun May 23 12:27:23 UTC 2010

Hi

As mentioned in the wiki, the "standard" dates to 1969. The interface dates to (at least) 1962. I would not be at all surprised to find that it's older than that.  My first exposure was on Bell system modems, which were showing up as surplus in the late 60's. The EIA standard was very much a "catch up with" effort as opposed to a "design to" document. 

No, Radio Shack did not actually issue any version of the standard. They operate at a level more appropriate to the standard than the EIA.

Bob

On May 23, 2010, at 12:26 AM, WB6BNQ wrote:

> Bob,
> 
> For the sake of propriety please don't propagate myths.  The RS- series of standards predate Radio Shack.  The wiki at the following address has a good write-up about it:
> 
> http://en.wikipedia.org/wiki/RS-232
> 
> And, yes it is standardized.  Although many have abused it.
> 
> Bill....WB6BNQ
> 
> 
> Bob Camp wrote:
> 
>> Hi
>> 
>> In this case the RS relates to Radio Shack ......
>> 
>> Not a lot of standardization in the RS-232 world. Take a look at the slew rate limiting requirements in the original document ...
>> 
>> Bob
>> 
>> On May 22, 2010, at 9:47 PM, Robert Darlington wrote:
>> 
>>> Was there ever a standard?  I always thought the "RS" stood for
>>> Recommended Standard, as in "you *should* do the following" as
>>> compared to "you shall do the following"  I've seen inverted TTL talk
>>> to the RS232 port on laptops and I even sometimes use the max233's
>>> (+/- 10 volts instead of 12), but always use the full max232 with
>>> external charge pumps when it's a gadget that needs to work everytime
>>> with systems from multiple countries.
>>> 
>>> -Bob
>>> 
>>> On Sat, May 22, 2010 at 7:21 PM, Didier Juges <didier at cox.net> wrote:
>>>> Bruce,
>>>> 
>>>> Thanks for the additional information.
>>>> 
>>>> +/- 14V is quite unusually low in my experience. I typically use Maxim parts such as the MAX220 series, which is specified at +/-25V for no damage on the inputs (some parts in that series go to +/-30V).
>>>> 
>>>> The bottom line is that as I pointed out earlier, there is no such thing as an RS-232 standard any more.
>>>> 
>>>> Didier
>>>> 
>>>> ------------------------ Sent from my BlackBerry Wireless thingy while I do other things...
>>>> 
>>>> -----Original Message-----
>>>> From: Bruce Griffiths <bruce.griffiths at xtra.co.nz>
>>>> Date: Sun, 23 May 2010 10:39:21
>>>> To: Discussion of precise time and frequency measurement<time-nuts at febo.com>
>>>> Subject: Re: [time-nuts] Z3805 utility, Was: AW:  (no subject)
>>>> 
>>>> Didier Juges wrote:
>>>>> Bill, I think you got it backwards. +/- 12V is typical for RS-232, 0/+5V is
>>>>> for RS-422 and RS-485.
>>>>> 
>>>>> No RS-232 receiver should be damaged with +/- 12V or even +/- 15V because
>>>>> that is their normal operating voltage.
>>>>> 
>>>>> Also, RS-422 and RS-485 have something like 25V common mode tolerance (not
>>>>> sure what the actual spec is there,) so that the RS-422 and RS-485 receivers
>>>>> should not be damaged by 15V either. The RS-422 drivers are pretty low
>>>>> impedance, while the RS-232 drivers are current limited, so I don't think
>>>>> that connecting an RS-232 driver into an RS-422 driver will damage either.
>>>>> 
>>>> Picking one RS485 receiver (ADM1485) at random the receiver absolute
>>>> maximum (no damage) input range is -14V to +14V.
>>>> The RS485 receiver operating common mode range is -7V to +12V.
>>>> RS422 receivers have an input operating range of -7V to +7V.
>>>> The no damage RS422 receiver input ratings may be higher.
>>>>> However, most recent (<10 years?) RS-232 receivers will work with a 0/+3V or
>>>>> 0/+5V input, conveniently having a threshold a few 10's or 100's of mV above
>>>>> ground, even though the original RS-232 spec required receivers that work
>>>>> with as low as +/- 3V, and drivers that deliver +/- 9V minimum. Many
>>>>> commercial systems use +/- 5V drivers for RS-232 (B&B Electronics sells a
>>>>> lot of converters with these voltages). This is a deliciously sloppy spec
>>>>> that nobody has met in the last 25 years probably, yet works most of the
>>>>> time.
>>>>> 
>>>>> The one thing to avoid is to short an RS-422 (or RS-485) driver to ground,
>>>>> as that can actually cause damage, maybe not every time, but definitely not
>>>>> recommended. These have relatively high current output capability to drive
>>>>> long lines.
>>>>> 
>>>>> Didier KO4BB
>>>>> 
>>>>> 
>>>>> 
>>>> Bruce
>>>>> -----Original Message-----
>>>>> From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
>>>>> Behalf Of Bill Hawkins
>>>>> Sent: Saturday, May 22, 2010 3:09 PM
>>>>> To: 'Discussion of precise time and frequency measurement'
>>>>> Subject: Re: [time-nuts] Z3805 utility, Was: AW: (no subject)
>>>>> 
>>>>> When all else fails, get out the voltmeter.
>>>>> 
>>>>> Do you have power to the antenna? Is it the right voltage? All the way to
>>>>> the antenna?
>>>>> 
>>>>> What volts are on pins 2 or 3 relative to pin 7 in the comm connector?
>>>>> 
>>>>> If you see 12 volts, that's RS-422. You may have burned out your computer's
>>>>> serial port.
>>>>> 
>>>>> If you see less than 5 volts, that's RS-232 and all should be well, unless
>>>>> you see zero volts.
>>>>> 
>>>>> I may have the RS-xxx volts somewhat off because my memory isn't what it
>>>>> used to be.
>>>>> 
>>>>> The guy you bought it from should be able to help with comm basics.
>>>>> 
>>>>> Bill Hawkins
>>>>> 
>>>>> 
>>>>> -----Original Message-----
>>>>> From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
>>>>> Behalf Of Robert Benward
>>>>> Sent: Saturday, May 22, 2010 2:08 PM
>>>>> To: Discussion of precise time and frequency measurement
>>>>> Subject: Re: [time-nuts] Z3805 utility, Was: AW: (no subject)
>>>>> 
>>>>> Hi All,
>>>>> I hooked everything up and I still get nothing.  I can't seem to establish
>>>>> communications  with the Z3805.  I tried a
>>>>> null modem as well, in case the cable (supplied) was wired with the wrong
>>>>> connector gender.  I see a green blinking
>>>>> light inside, it he left rear corner of the box.  Everything is warm, but
>>>>> nothing else.  Any ideas?
>>>>> 
>>>>> Bob
>>>>> 
>>>>> 
>>>>> 
>>>>> 
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>>>>> 
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>>>>> 
>>>> 
>>>> 
>>>> 
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