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Ring detector

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MikeMl

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http://www.jakeselectronics.net/images/projects/telephoneringdetector/schematic.jpg


In this link what would be the output logic of circuit and why output of this circuit fluctuates as input?
First, to ask a new question, start a new forum thread instead of appending to an old thread...

Second, is the circuit you posted supposed to be a phone-line ring detector? If it is, then it would make the US phone companies very unhappy; unhappy enough to disconnect your service. The circuit is referenced to ground. Big n0-n0. Niether side of a phone line must have path to ground. A ring-detector circuit must not put a dc load between the two sides of the phone line. Has to have a DC blocking capacitor,

The original circuit posted in the 2003 thread meets the US and Canadian requirements. Yours does not. I have no idea what the reqirements are in Nepal...
 

crutschow

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.....................
Second, is the circuit you posted supposed to be a phone-line ring detector? If it is, then it would make the US phone companies very unhappy; unhappy enough to disconnect your service. The circuit is referenced to ground. Big n0-n0. Niether side of a phone line must have path to ground. A ring-detector circuit must not put a dc load between the two sides of the phone line. Has to have a DC blocking capacitor,

.................
066bex408's circuit would be OK isolation wise as long as the ground indicated is an isolated common on the circuit board and doesn't go anywhere else.

But it should have a series capacitor (or remove R1), as you stated.
 

066bex408

New Member
I'm trying to make system to control the home appliance using PSTN. I'm thinking about the feature of security so that system call or send message automatically to the owner. There will need DTMF encoder but without keypad pressing how DTMF signal or tone be generated?
 

crutschow

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I'm trying to make system to control the home appliance using PSTN. I'm thinking about the feature of security so that system call or send message automatically to the owner. There will need DTMF encoder but without keypad pressing how DTMF signal or tone be generated?
You can use a microprocessor or other logic circuits to activate a DTMF IC generator.
 

066bex408

New Member
how the number stored in microprocessor can generate the DTMF tone for automatic call because there will not use of keypad...........
 

Mr RB

Well-Known Member
The microcontroller can generate binary codes 0-15 on 4 output pins. Those 4 pins go to the DTMF tone generator IC, which makes the tones. Browse the internet for tons of circuits. :)

If you want to use less parts and a bit more work, the microcontroller can generate DTMF tones directly, which is done mathematically and only needs a resistor and capacitor on the PWM output pin. Then no DTMF IC is needed.

Here is a page that shows how to do it that way;
http://www.romanblack.com/SG/SG_tutorial.htm#DTMF
(see Tut13, near the bottom of the page)
 
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