- This circuit was designed by Tim Jackson at 1990. It was presented in his article "TELEPHONE LINE SURGE ARRESTOR" found in telecommunication archives.
The trick is to install the unit in the line between the telephone jack and your modem (ie: not too far from the modem, like in another room) and connect the earth lead from the circuit to the earth pin on the SAME PLUG that feeds your PC. The phone line has a gas arrestor from each leg to earth. In other words, two gas arrestors. One from A to earth and one from B to earth.
The line then has a resistor in series with each leg (A and B) before being connected to the TISP2290 (the Texas Instruments chip mentioned earlier). This chip has three pins. The outer two (A and B in the diagram) are connected to the resistors while the centre one (C) is connected to earth. The metal tag of this component is internally connected to the earth pin (C), just for the record. The modem is fed from the outer two pins of the TISP2290.
The bulk of the energy involved in a surge is dissipated by trusted (and slow as treacle) gas arrestors. The TISP2290 absorbs the high speed spike that the gas arrestors miss and is itself protected by the two resistors which provide a little current limiting. The modem, being fed from the same point as the TISP2290 is protected by the whole circuit.
For those who have to know, the TISP2290 works in a manner similar to a zener array connected between the A and B wire and earth so as to limit the voltage between any of three points to about 200 Volts. As you know this is not entirely effective and so if the voltage rises to 290 Volts (hence TISP2*290*) then this crafty critter cuts in triacs to crowbar the offending points to earth until the surge has passed. - Furse ESP-TN
This circuit is a circuit diagram of commercial surge protector sold under name Furse ESP-TN for protecting normal telephone lines. The circuit is designed for protecting normal telephone lines and is packaged to metal box where there are connectors for telephone line and thick ground wire (the connector in the bottom of the circuit). The components were installed to circuit board where there is lots of copper thickened by lots of tin. The circuit uses on 260 V doube gas arrestor as first protection. After that there is 2.2 ohm series resistors followed by surgesuppression network built from 180V TISP and three DVRs. After that there are two more serial resistors and network built from three 180V zener diodes. Wuite complicated circuit and no wonder why it costs quite much (about 100 US dollars). - Telematic Lighting Arrestor SAPN (Telematic Surge Barrier)
This is another telephone line surge arrestor sold under name Telmatic SAPN Line Barrier by Black Box. The protector has following specs:- Clamping voltage: 200V+-10%
- Rise time: 15 ns
- Interface: 2-wire PSTN
- Connectors: Screw terminals
- Size: 2.5H x 2.1W x 14D cm
- Weight: 0.1 kg
- Protection mechanism: 5 kA gas discharge tube and high speed clamp diodes