Inferno #01
31 декабря 2000
  Железо  

Shelezyaka - the prefix to the phone: the phone line signal amplifier.

<b>Shelezyaka</b> - the prefix to the phone: the phone line signal amplifier.
        Amplifiers

         TELEPHONE LINE



(C) Michael Shulgin / Bubantus Software
Search and edit by Penetrator (VFHB)
Add by Shaitan / Stars of Keladan

 Oddly, but among spektrumistov
began to develop a positive trend toward modemizatsii their 
computers. Most people in our country have a modem with the 
speed at 2400 baud and so you have to spend long hours in front 
of the monitor in anticipation of fresh files, and if still 
remember about our "Quality" phone lines, then another 
connection is converted into a torture. One reason may be bad 
konnekta serve not only the presence of noise in the channel, 
but also a very low level of the signal. But do not immediately 
rush to collect the scheme, first remove the capacitors for all 
telephone jacks in your apartment, since their presence greatly 
reduces the signal (We know from personal experience).




    Concept.


                                  ----
                                  / \ / \ / \

                                  L1 R1

                    R2 +15 At 7

             VS1 +

                                     - DA1

              > <-15V, 4 June


                                   3

                           R3

              VS2 about

                                   2

              > <1 8 C4


            C1

               C2 R4



                           C3

                          + C5



           K Line



            Details

 DA1 - 544UD2A, 153UD2A, preferred
operatsionniki with high input impedance and high speed.
 L1 - DP1 ,2-400 (may be absent,
IMHO);
 R1 - 22 ohms;
 R2 - 33 ohms;
 R3 - 160 ohms;
 R4 - 1,6 kOhm;
 C1, C2 - 4.0 uF voltage not less than
60V;
 C3 - 20.0 uF (possible electrolyte volts
20);
 C4 - 180 pF;
 C5 - .043 uF
 VS1, VS2 - any bilateral zener at 18-20 V, for example, 3 
series-connected KS162A. 



           Food

 The more stabilizirovannoe - the better.



          Appointment

              and

      operating principle

 The amplifier is a device
(Dipole) with a negative differential resistance, plug
parallel to the telephone line and allows you to compensate for 
the attenuation efficiency signal (from the remote modem) on 
the line resistance by increasing the input resistance 
equivalent to your modem. Negative resistance is created by the 
PIC, which covered power through a chain R1L1 and capacitor C3. 
The depth of the PIC may be regulated by the resistance R1. 
Elements L1, C4 prevent self-excitation of the amplifier at 
ultrasonic frequencies, C5 - is introduced to correction of 
frequency response. C3 prevents self-oscillation at infrasonic 
frequencies. Ctabilitrony VS1, VS2 prevent the output from 
operatsionnika down at the line surges

(For lifting / lowering of the tube set
rooms). BOTH must be present, otherwise the chip sooner or 
later be burned. Capacitors C1, C2 - dividing.




          Establishing

... First of all, locate the line on which you will not be beat 
for a squeak and growl in her stage set-up;)))

 Who does not have an oscilloscope: Power
connected to a line parallel to the modem,
and polarity is not important. By setting R1 to the minimum 
resistance, you when off-hook will hear a deafening whistle. 
All right, this means that the scheme operates in generation 
mode. Increase the resistance R1 to those

long as the whistle will not disappear, but useful
signal line (not the buzzer!, better to try to voice) will not 
appreciably increase without changing color of sound 
(underlining the higher frequencies and distortion loud 
sounds). May need to pick up capacitance C4 and C5. By the way, 
and C3 should be connected exactly as in the diagram. Temptation

connect it to the top (the scheme), the output C2, reducing the 
capacity of up to 3 uF, but thus decreases the gain and appears

Fatal infra generation.
 Who has the oscilloscope: Connect
scheme exactly as in the first case,
and under the supervision of the incoming waveform
signal to achieve the absence of restrictions
at the peak, distortion, a "step" and "ringing" in the 
amplification of pulse signals. Strengthening the input signal 
while maintaining an acceptable level of distortion is about 
60% of the theoretical, ie about 2. I got this:

line impedance 660 ohm input impedance of the TA - 260 ohms, 
the amplitude of the signal - 1.1 V. At full compensation of 
line resistance gain was about 3, but this was accompanied by 
limitation and ringing. Eliminate the past, succeeded in

amplification of about 2.



      Work with the modem.

 NOTE: The amplifier is designed to work
ONLY when the signal from the
remote modem is so weak that
its carrier is not recognized by your modem,
and, accordingly, fails. At the hearing, it looks like an 
infinite "piii-sshshshsh-PIII-SSHSHSHSHSHSHSHSHSHSHSHSH ...". 
Basically, if the line is quiet, this sin couple Sportster - 
Zuhel. If the modems are adjustable levels of sensitivity and 
output, the amplifier you'll probably also be required. In any 
case, using described the amplifier I was able to almost 
completely solve the problem of disconnection. Fit amplifier is 
reduced to a modem podbru of R1 engine for In order to obtain a 
stable connection with error correction (if your modem supports 
it) and, possibly, the greatest cps. With a large R1 (shallow 
PIC), you can not get a tangible result (Connect will not 
install). For a small R1 (in the case of overcompensation) 
increases dramatically the percentage of connection to the ... 
/ NONE (up to 100%) and errors in the admission due to signal 
distortion. In general, if you get tired of listening to 
infinite peresvist modems, and must connect, try ... Yes, it is 
not necessary keep it under a power in the handset - in this 
case it generates in line, but it may be wrong

understood by the PBX. Unfortunately, we do not have statistics 
on the RX and SNR, as My sportster does not support the 
issuance of these statistics. Nevertheless, I

represented fragments of statistics obtained log analyzer T-Lan:



             Without the amplifier:

   (7.11 1:55:28 - 25/07 21:05:58)


                Password: '*' - Present,

                '' - Absent, '?' - Error

                Outgoing calls

                Sessions

                Last Session Result:

                '·' - Success,''-

                Aborted

P C S L Address


* 453 53 · 2:5020 / 347.0


  Days / Time Bytes Bytes CPS

  Online received sent


  6:03:18 2653225 87418 125


             With the amplifier:

   (25/07 21:06:22 - 31/07 23:14:18)



    P C S L Address



    * 44 12 × 2:5020 / 347.0


   Days / Time Bytes Bytes CPS

     Online received sent


      1:17:47 999536 27495 220



  I recommend to pay attention to

         ratio of C / S.







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