VICOMM - compatible modem
with transformerless isolation from the line
(shortened version of the article
http://savc.op.ufanet.ru/vicomm/vicomm.html)
* Does not contain a transformer or other inductive elements
* The transmission speed is limited only by the software
* Hardware and software compatible with VICOMM
* Digital signals for communication with a computer
* Galvanic isolation from the line
* Incoming call detection
* Program line occupation
* Pulse dialing
Development began back in 2000. Exactly
then the idea came into Anton’s bright head - to make a modem for
speca compatible with VICOMM, but without transformer. Stripe
operating frequencies for such a modem are not limited from below, but from above
limited only by the software and the quality of the telephone line. Question
was in high-voltage ontonapax. Then we managed to find suitable ones,
and it was KP249KH5A.
In 2002, a trial copy of the modem was assembled.
In the original circuit, a signal was received using
comparator But, as it turned out, it works unstable - too
the gain factor is high, difficulties when working from
monopolar nutrition. Therefore, the receiver circuit had to
replace with one transistor. And it works flawlessly.
Modems were tested with the MACRO MODEM program - file transfer
runs without errors in all modes, up to speed 9600.
The driver did not support higher speeds. They drove floppy disks back and forth,
chatted. Moreover, I (SAVC) live in the Ministry of Internal Affairs, and Anton (TDD) in
Sinailovo. Who lives in Ufa will understand thisdifferent parts of the city.
There are approximately 100 km between them.
After such success, I tried to write a driver for large
speed. But I went too far with optimization and didn’t finish it
work to the end. In addition, the interface with the driver is built on
in my opinion, not thought out. This is somewhat depressing.
In general, my experiments with the modem led to the birth
dialers - TELNUM programs.
The modem is connected to the computer via one 5-pin connector,
to which control logical signals and power come. C
nutrition makes everything clear. A little about where to get signals
management. As you understand, on different computers they are located in
different places. I will give general recommendations on how to find them in
yours.
The control signals TXD and LINE are taken directly from the corresponding
pins of the microcircuit that outputs to port #FE. RXD signal
goes directly to the microcircuit that operates as input from
port #FE. Signals are LOGICAL. Therefore the schemesformation
The signal to and from the tape recorder must be turned off. Instead of
tape recorder 3-pin connector, install the same one with 5
conclusions. On your computer, find the #FE port register (usually
TM9). Identify and disable the signal conditioning circuit,
entering the tape recorder. Instead, the signal from the register output
will go to pin 3 of the modem (TXD). The same microcircuit has one of
triggers are not used, although connected to the data bus per line
D5. So, the output of this trigger will be the LINE signal for
modem, it must be connected to pin 4 of the connector. Now you need
find a microcircuit that works as input, usually KP11. Disable
from it a comparator and apply a signal directly from pin 1
connector.
Sergeev Andrey Valerievich aka SAVC
savc@ufamail.ru ICQ 244 368 763
Dokuchaev Anton Vitalievich aka TDD
skydragon@list.ru
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