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.
