Move #10 04 сентября 1997

Железо

Iron - Galvonicheskaya junction with the telephone line in the C-DOS modem.

Iron. Galvanic isolation of C-DOS modem.


Dr.Livsy / city Koydanovo /, Ars

    In this article, your attention is invited to a simple
refinement of C-DOS modem solves the problem of galvanic
interchanges with the telephone line.

    Indeed, the main glitch circuits, which has long
time was left, in particular, a sysop. Although
that the node dialing closely follows
AON'ovskoy ordinary scheme, using it in the modem shall
some unpleasant moments. They stem from the fact that the 
computer Unlike AON'a has a lot of external devices:

Monitor (often - TV), power bass, for which
often used stereokompleks), etc. And here
device? And besides, that all adapters have soednitelnye
common wire, and "land" is and the input diode assembly
Modem ... The result comes to a curious situation: it is 
required pull the plug the TV cable from the socket, turn off

adapter to the amplifier, turn off the monitor, etc. Of course,
Even if you do and do not ground the unit, anyway,
"Cursed land" makes itself felt a high level of interference
telephone line.

    Of course, the noise level can be significant, if not 
entirely, weakened if the throw from the circuit load diode 
bridge - it resistor R14-1 (1,2), MW (see Figure 1), which is 
on the board near the phone size sockets and two high-voltage 
capacitors, average of 3 parallel standing on the board 
resistances. His Color code: brown / black (red) / green. If you

not going to open up their BBS'ku, then this would be amputation
enough to get rid of the background in the line, though
galvanic isolation still will not.

    Another thing, if you open BBS'ku. It immediately
problems in responding to the call modem. View
no load, modem sometimes refuses to pick up the phone.
Well that is concerned, this "trifling problem, a desire to open
its BBS'ku is an incentive for its quick resolution.

    In addition to program completion (simplification) of 
interview procedures call in the C-DOS'e was proposed and a 
number of circuit decisions. Suffice it to recall 
Stinger'ovskie zener and Hamer'ovskie relyushki. Me more than 
anything, Ars'a, struck Layer. He built carry a small 
mechanical pribambas consisting of bell system from the hard 
disk device connected to a pair of wires with entrance poll 
call modem. I think we should explain how this device worked, 
what to say - really brilliant! I say this without any share of 
irony. 

    Our people are very talented, and if everyone could (would,
had the opportunity - do not even know what the word here is 
better suit) to reveal themselves, then about any crisis of 
Spectrum, the which in recent years have suddenly faltered, 
speech, and there was no be. Those who loudly call themselves 
cool zhelezyachnikami, encoders, etc., beating their breasts 
and / or tearing itself shirt are, to put it mildly, ordinary 
rattle up until they prove their "if ... ... you need to

was ... "in fact. And, unfortunately, lost.

    Again, I digress from the topic, all go directly to the
refinement.

Subject to finalization of the following sites:


a) Input circuit:


                       to internal Fig.1
T1 __ K1.1 chains

  ______/ ____________ ____________X1.1 __
 (3 ~ / \ __.___/ ___.__
 (___ / VD \ Normal. ====>
 (+ \ 7 / (\ / X1.2

  4 KTS407A ~ ___ C5 0,1 uF C11 *

                ___ 160 0.68 uF

                R14 1M 160


Removed from the scheme VD7 diode bridge and resistor R14. 
Parallel contacts of relay switches high voltage capacitor 
(with a working voltage not less than 160 in) capacity of 0.1 
.. 1.0 uF. 

b) scheme of the dial and connect to the line:


                                   ___

                 VT4 KT940A ___ to the cathode (-) VD7
15 pin. ___ _ / To R11 680
IC D2 ___ \ e removed from the scheme:
KR1533TM8 R10 2,7 K b \ ____ VT4, R11, R10.
(Bit 6) Figure 2



                                    K1 REC-49 (0301)

                    R7 330 b> 5 in
7 pin. VD6 * ___ _ / a
IC D2> ___ \ e VT1 <
(Bit 5) VD7 * ___ \ ____ KT940A VD3, VD6 *,

             > ___ VD7 * - KD522A
15 pin. R15 * 330 ___ R16 * 1K
IC D2 (bit 6) ___ Fig.3


    Minor clarifications to this part of the improvements. 
Instead of two transistors are now used alone. Old site dialing

completely removed, and the node connecting the modem to the 
line (Figure 3) expanding the scheme with the help of OR, such 
as diode logic. 

From the old scheme used the resistor R7 (all of the additional
items marked with *). Dialing now made
no transistor VT4 (Figure 2), trailing on the ground the 
cathode of the diode Build VD7 through resistor R11, and 
neposredstenno by the relay. Ie as a load used input winding 
(3-4) transformer T1 (Figure 1). However, now, bits 6 and 5 in

OUT are absolutely equivalent, but it is - nothing.


    In principle, users can once again stay at this
paragraph. If you want to use the server mode, it should be
even solve the problem with the chain ring.



c) scheme of the survey ringing (call).



  to vyv.15 IC D1 (K561LN1)

  <

      R12 10K R13 200K C4 0,1 uF

       ___ ___ 160 in Fig.4

       ___ ___

                                   to (-) Old Scheme node

        >>> 5 in VD7 (Fig. 4) is replaced

     VD4 - KD522A - VD5 a new one (Fig. 5).



                                          to the pin. 15 D1

                                           >

       at UD  KT315B R18 * 30K

  2 Figure 5 +5


    After making all these improvements to the telephone line
is connected only input winding
transformer. All other processes will run only during
secondary circuits.

    Unfortunately, apparently, this revision does not solve the 
problem long-distance communication. Yet there should be more 
reason to seek in the channels of transmission, rather than 
modems. 

    This revision, among other things, is the only
proposed by me for all 8 months of the dial-up network.
Despite the huge amount of criticism of the scheme modem in 
Minsk not one person who could advise

anything sensible. Well, what is usually waiting for 9 months! 
.. :-) 


    Finally, I came up with this idea. Nearing New
Year. :-) So, why not decorate a fee holiday
garland ... In general, announced a competition for display unit
modes of the modem. Write to MOVE, offer their ideas,
improvements, and maybe we'll meet again in this column.