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|Have you ever been using the modem or fax and someone else picks up the phone, breaking the connection? Well, this simple circuit should put an end to that. It signals that the phone is in use by lighting a red LED. When the phone is not in use, a green LED is lit. It needs no external power and can be connected anywhere on the phone line, even mounted inside the phone.|
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|I am simulating this circuit in LTSpice, and it does not work. The LED drop voltages are not what they are supposed to be. As one comment here says, both LED's are on at the same time. Simulate the circuit with LTSpice and find out that the circuit is bad. Plus, LTSpice shows that circuit draws 2.25 mA when telephone is not in use! This is colossal current! You will have telephone companies contact you thinking that you use power for free for non-telephone needs (lighting, etc). Do simulation before buying and building. Simulation took me only about 1 hr to create.|
|WARNING ! Modern phone lines require a load resistance of ten megohms. The older relay systems would work fine . Your phone will indicate "busy" at all times. You cannot put any load on a new system in the of-line condition. You will have to use a wall-wart transformer to power any of-line system. 10 meg ohms impeadence required to be off line. Basicly , try it , you will find out. .. LHB.|
|plz send me the complete discription and how can i make this circuit.... some one saying in comments "that this circuit didn't work, but after some minor adjustments, it did seem to work just fine. Nice circuit." so plz tell me whats the minor adjusment u done???? plz give me reply as soon as possoble|
|I originally posted that this circuit didn't work, but after some minor adjustments, it did seem to work just fine. Nice circuit.|
|Hi, I have been trying your project but it doesn't seem to be working for me. Mine just has both LED's Stay on constantly. Do different phone providers affect this, or possiby newer phones? Also I did switch the 1.5 Amp 250 PIV Bridge Rectifier because I could not find it with a 1.5 Amp 400 Volt Bridge Rectifier. I dont think this will make a difference but if it does please let me know. Do you know where I could find a 1.5 Amp 250 PIV Bridge Rectifier? Thanks|
|I have tested that circuit and it works great. LED are dim. use 2N3904 or 2N2222 The only problem I had is that I did not have the right diode for my bridge rectifer. 1N4148 did not work. I then use four 1N4001. It did work, the LED light up nicelly but you could not call!! I measure the voltage and got 48V. I live in Canada. The damn circuit is voltage divider! Do you homework, we will not do it for you. Stop asking questions and build it! It will cost you 1$ in parts!|
|This circuit may work well, but it draws too much current from the phone line when it is idle, causing the central office to think that there is leakage on the line. I strongly advise you to not use it, instead use the one at Bowden's hobby circuits (google for it). Bowden's draws much, much less current when idle.|
|tell me that how i make the major project with combine this project to the other like that ringer, busy indicator and more in telephones. and plz tell me the combined circuit to make the major project and inform me about the components used|
|i want ot know the complete description of parts and working of Phone Busy Indicator.also i want assurance that when implemented on pcb it works well..tells us about another ic no of npn taransistor because the spicpied one is not available if phone busy indicator work on them then tell us....Hi! im jake. can u help me with my project. How can i determine if i call then the receiver is answer the call? waitng for reply..... WANT TO KNOW HOW THIS CIRCUIT IS WORKING IN DETAIL ,ITS APPLICATION...plz do mail me all decriptions n details widin two days to mine mail id|
|i want ot know the complete description of parts and working of Phone Busy Indicator.also i want assurance that when implemented on pcb it works well.|
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