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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