Inferno #01
31 декабря 2000 |
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Shelezyaka - 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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