,s%$%s, $$7"^"?$$L i$$',d$b,'$$; yyyyyyyy$ $$$$$ $$l Away noodles ! ^^"""' '%$%',$$F by rost ,s$$?;,_ __,,__ '?$'j$$$$%syyyy$""^" ^$$$"^ Despite of all the big availability and a wide circulation of the allocated lines, dialup is not so fast surrender as many predicted. However low speed of data transmission, and basically on fault of a telephone system strongly breaks off. The purpose of the given small review is to collect in a heap, to make, so to say, compilation of experience of mankind in struggle for improvement of quality of modem connection, instead of to invent that that absolutely new (as it simply not so probably in narrow frameworks of a wire telephony). The author does not apply on copyright all given circuits, in the majority they are taken from different sources, I do not remember already from what. So - the main enemy - poor quality of native telephone systems. As is known, in multicomponent systems quality is defined by the worse part. Let's try to consider these parts more in detail and to decide as we can improve them. Unfortunately the interval from automatic telephone exchange up to your distributive panel does not give in to positive changes, as well as a head of the head of your telephone company, and is a pity. For this reason till now in territory of the former USSR of full analog telephone exchanges with awful quality, besides unreliable, noisy, suxx ... We shall try to improve parts from panel up to the modem. First of all - AWAY NOODLES! First from ears, then these shaky postings, not with it is simple them so have nicknamed. To replace them on SHVPT (rus kind of wire decalared) or something similar it is no expensive, and work of the modem begins realy good. All contacts it is necessary certainly resoldering, not any twistings. If we already also have dared to replace a wire then distributing we shall make on competent. We pull a wire all over again to the modem, and then already is farther - to phones. I.e. from the beginning the signal goes in input LINE of the modem, and from output PHONE he goes to the rests devices. It is necessary to check up - whether disconnects the modem output PHONE at the moment of connection. If is not present - it is necessary to put the toggle - switch after output PHONE and to disconnect phones (or what there at you?) during using the modem. What for? It will relieve target cascades of the modem of superfluous loading. If on the modem only a telephone input, so the switch should be put on the socket in front of the modem. Tumbler will switch the modem/phone. And already from this socket we shall pull two wires - one to the modem, another to phones. \bonus\circuits\circuit1.png At due skill in management of a soldering iron it is possible to create such circuit automatic telephone blockirator's: \bonus\circuits\circuit2.png The majority of similar circuits on dinistors (rus kind of transistor) or tiristors (too kind of transistor), have advantage as simplicity, but have as well minuses, such as: resistance at switching, "ringout" on parallel devices and is usual with observance of polarity. The delay of switching, at use given circuits, makes approximately near 1 sec, due to use of the 'relay' resistance of connection is reduced also, observance of polarity is not required. The relay is better for applying 'gercon' (because of the noiselessness) on 5-7 volt, but probably it is required adjustment of the resistor, and in quality diod the bridge it is possible to use 4 diodes KD522B. Now we shall try to amplification and then to filter a signal. The amplifier would be more logical to establish in distributive panel, but there he can to someone it is not pleasant, or on the contrary very much it is pleasant, in general will cause a heightened interest and will disappear. The exit from this situation arises - to arrange the amplifier, and at the same time and blockirator with the filter in one case. For the beginning we shall make a power unit for the amplifier. We shall take advantage of that in a telephone system already there is a constant voltage in 60 volt. We need two polar power supply by a voltage of 15 volt. Easy to make it under such circuit: \bonus\circuits\circuit3.png The microcircuit can be applied and another, for example 7915, only it is necessary to take into account that she stabilizes a negative voltage, accordingly it is necessary to change and the circuit. Disseminating capacity on a microcircuit in this case not big, it is possible to do without and a radiator. At replacement by other microcircuit pay attention to the maximal entrance voltage of the given microcircuit. It should be not less than 30 volt. Condensers anyone electrolits, a voltage not less than 16 volt, is better 25. Resistors 50...150 kom (0,25Vt). Diod bridge - as in the previous circuit. The circuit of the amplifier present on \bonus\circuits\circuit4.png. She represents the amplifier with a positive feedback. It is established on phone line in parallel the modem. amplification in 1,5. 2 times. Operational amplifier DA1 it is possible to use anyone, taking into account purpose of conclusions. It was used 553UD2 in plastic DIP. L1 - Any throttle on 200. 400uH. It was used DP1, 2-400. R1 - Adjusts amplification. VS1, VS2 - symmetric stabilitrons on 20V for protection DA1. Were applied 2 consistently connected KC210B. Condenser S3 is included by plus on the ground. Adjustment: If there is an oscillograph, at the included feed and connected phone lines (the tube is lifted!) presence of generation on a conclusion 10 DA1 is checked at extreme left under the circuit position of cursor R1. Gradually increasing R1 to achieve loss of generation. This position R1 corresponds to some threshold level of amplification. For stability to add 5..20 % to current value R1. All these operations can be done without an oscillograph on hearing, having connected the parallel device, but it will be necessary to take into account additional loading in a line. Final position R2 - at concrete connecting. The important remark: At the put tube the circuit generates a voice-frequency signal in a line. Therefore it is desirable to disconnect a feed (to provide the switch) when the tube is put. If to you laziness work with all it it is possible to get the ready amplifier executed in the telephone socket, such now are sold rather cheaply - about 150 roubles (russian many ;) ). That basically it is equal to the cost price of the given circuit, taking into account expenditures of labour. However any experience :) Let's proceed to creation of the filter. Some circuits: 1. \bonus\circuits\circuit5.png C1: 1-1.5 mkF x 200V R1: 10 kom (rough adjustment) R2: 2 whom (exact adjustment) R3: 100 Om x 0.25W In break of a circuit between C1 and a line it is possible to establish the switch if necessary to maintain your system without use filters. 2. \bonus\circuits\circuit6.png The circuit is primitive filter of average frequencies. The lightdiod displays connection of the modem to a telephone line. The circuit freely can be arranged in the case for the telephone socket, and lightdiod fastens from above on glue in an aperture of the case. As adjustment of resistor Rn can be demanded, he limits a voltage through lightdiod and in part influences parameters of the filter - depends on type of the modem and automatic telephone exchange, average value near 100. At connection it is necessary to observe polarity! 3. \bonus\circuits\circuit7.png There are still more many circuits with use of coils of inductance. I to do make them did not try, if to whom it is interesting, can find the circuit independently. Or to calculate, that it is more interesting. If and to be engaged with coils of inductance i.e. if you count yourselves elit phreak man it is possible to climb in the modem. The matter is that on inputs of the majority of modems there is a transformer sharing a signal on variable/constant currents. His quality usually happens very low, especially it concerns modems more cheaply 50$. It is possible to buy good and to put instead of yours, but he costs about 10$ and not always he still can be found. We shall make his: It is required 2 armored cups from ferrite of mark 20001, 20002, 20003 (the best variant), external diameter 32 mm, the plastic coil - the core under them and wire PEL 0.16 (it is possible 0.15, but it turns out hardly worse) and an insulating tape dark blue (!!) colors. Manufacturing: Attention! All parameters are given at the rate of overall dimensions of the core! On the core the initial winding is reeled up - 450 coils of a wire, then 2 times is wound by an insulating tape (that the distance between windings made ~0.8 mm). Then it is wound 500 coils of a secondary winding. From above again it is rolled up by an insulating tape that the wire was not unwound. The coil - the core is inserted into armored cups - the product is ready. Way of connection of half and payments gets out proceeding from features of a payment of the modem. If there is an opportunity to drill payment - drill and fasten the screw. Only do not overlook cardboard linings between the transformer and a payment that cups have not bursted. If to drill it is impossible, stick together cups the supermoment, and a method of fastening to a payment think out. Connection very simple - an initial winding to a line, secondary to the analog-digital converter. Perhaps and all basic improvements which can be made. good luck.