Security

Protection For Telephone Line

A long time ago when telephones were so simple almost nothing could go amiss from an electrical point of view, Telecom operators installed surge protection on all telephone lines exposed to storm risks. Paradoxically, now that we are hooking up delicate and expensive equipment such as telephones filled with electronics, fax machines, (A)DSL modems, etc., this protection has disappeared.

However, if you have the good fortune to live in the countryside in a building served by overhead telephone lines, there’s an obvious risk of very high voltages being induced on the lines during thunderstorms. While we have lost count today of all of the modems, fax machines and other telephones that have been destroyed by a ‘bolt of lightning’, surprisingly you only have to invest a few pounds to get a remarkably efficient protection device like the one we are proposing here.
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Author: Christian Tavernier – Copyright: Elektor Electronics Magazine
Source:http://www.extremecircuits.net/2010/05/protection-for-telephone-line.html

Be the first to comment - What do you think? Posted by admin - August 27, 2010 at 6:49 am

Categories: Security, Telephone Tags: surge protection circuit, telephone line protection, telephone line voltage

Overload protection circuit

Generally the level of a signal that departs output of sound signal generator the all. The that get fix have standard same score be 1Vrms. But in now audio signal generator the all the that may produce come to exceed limitation standard of the level input of stereo power amplifier. Thus have to have Overload protection circuit, for protect a part amplifier and a loudspeaker are damaged.
From circuit that picture when have input voltage resistor R1 perform current limit preceding still diode D1-D4 , build model Full wave rectifier circuit, for change ACV come to be DCV. By still be Input voltage give with transistor Q1 be when input voltage level (Vin) exceed tall 1 mV RMS. The transistor work be like something through the circuit. Then make have no volt signal pass by give with output (Vout).

You can buy Speaker Protection Circuit Kit
Convenient and effective course.

Be the first to comment - What do you think? Posted by admin - May 29, 2010 at 2:35 am

Categories: Electronic Control, Security Tags: loudspeaker protection, overload protection circuit

Car Burglar Alarm system with radio wave signal

When steal open automobile door relay K1 and K2 work make have voltage 12V give radio transmitter and origin sound part for mix radio waves steal will deaf anything sound. Because radio high frequency. But car owner will hear the sound , by take handbag very small radio, tune the frequency directly with the frequency of a transmitter. Which there is just not mW as a result the enough. A transmitter will still work for 15S (fix the time has with R3 and C1) although the door will open then follow thereafter radio transmitter will stop to work. Because of Transistor stop bias relay contract K2 be scratched. The transistor that use must durable current change relay get. If use battery separate separately and use an antenna model to draw start up the motor this use within a car , steal will can not cut the work has of from the outside.