Chris Arndt wrote:
>What's the baud rate of the 5v data? At the switch, convert it to rs232,
>plug it into something like a GridConnect Net232
>http://www.gridconnect.com/net232.html serial to ethernet adapter.
>
>Do the same at the other end, in reverse, plus add power back onto the
>data for the phone. Run a parallel POTS to POTS VOIP link. Not quite
>plug-n-play as the Net232s require setup for the network connections,
>and you'd probably have to port forward through the firewalls.
>
>That would be pretty cool, to have a 7130 from my 123211D home on my
>desk at work...
>
>Digital might be able to be done the same way, minus the POTS/VOIP link.
>Bits are bits...
>
>Hmmm....
>
>Larry wrote:
>
>
>
>>would be easy for apits, pair one is a pots loop (put it on voip). pair
>>two has power (get locally) and a 5v data stream to lite buttons and
>>detect button pushs.
>>
>>
>>
the apits is something like 1ms pulses, the dpits burst is in the 100kHz
area. That's the problem, the lamp/button data is async bidirectional.
The ksu sends a start followed by about 22 data bits, like the old
teleprinter data. the bits are 0 or 1 which is shifted into a latching
register that lights the buttons, beeps the speaker tones. The set then
follows the ksu data with its 8 or so bits indicating the status of the
buttons (up or down). The ksu sends the next station data and collects
the buttons for it. seven stations later it's back to the first station
again.
When they added the digitized audio, they stuffed it in the "open space"
between the old data stream. So there are two data rates, and a real
sync problem since the station "replies" to the ksu data. Been a long
time since I looked at the datastreams, so I can't tell you the exact
time periods. You can couple a 10k/10k audio transformer with a .05mF
cap to pair two and watch it on a scope. Almost all manufacturers
started with this basic lamp/button data stream, with some interesting
variations. some used two transformers, one on pair one for audio, the
other on pair two for data, and used center taps to "phantom" the power
to the station. others used pair one for pots like audio - ring voltage
and superimposed the 5v data onto the 20-40vdc power on pair two. pano
uses this on the apits with a pulse transformer to inject/recover the
data from pair two. the original kxt1232xx sets were single line phones
with the digital addons to lite and read buttons. the power fail switch
proves that real fast, when on, the set is a slt (with ringer!)
other manufacturers played some interesting tricks, use the same data
pair for two stations, by flipping the pulse polarity. station 9 used
the same ksu data port as port 1, but the ksu jack flipped the pair
polarity. A flipped line cord made the buttons on one set control the
line it's paired station was connected too ;-)
I had some forth programs that would read lamps and send button presses,
we used on some smart home projects back in the mid 80's. find the owner
from the co line and station lamps, set up calls/conferences then call
the boss. (see ieee spectrum 5/85, if you can find a copy ;-)
-lary / dallas
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