How to fake a dial tone using a PC?

• Aug 12, 2004

• #1

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david90

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I have this device that only works if it is connected to the phone jack and hears a dial tone.

On my pc I have a program that generate the dial tone but how would I go about connecting this device to my pc so that it hears the fake dial tone?

 

• Aug 12, 2004

• #2

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vfone

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telephone tone generator

If your program was made to work with PC sound card, try to connect to Line In/Out of the sound card.
regards

 

• Aug 12, 2004

• #3

U

unlving

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simple dialing tone circuit

vfone said:

If your program was made to work with PC sound card, try to connect to Line In/Out of the sound card.

Click to expand...

Not the audio phone jack , the Telephone jack

 

• Aug 15, 2004

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cherrytart

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fake dial tone generator

If your device acts like a telephone, it may expect to see the negative 48 volts that the central office supplys. Fortunately, most circuitry used in telephone equipment is very forgiving, sometimes requiring as little as 5 volts.

If you have to supply a voltage, you will not be able to safely connect to the sound card without some precautions, such as decoupling capacitors. Any decoupling capacitors on the sound card are probably low voltage.

 

• Aug 15, 2004

• #5

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Rayengine

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fake dial tone

Telephone lines grounding and PC grounding are different, made such isolation between two systems; otherwise telephone company will find you on the damage of network.

 

• Aug 18, 2004

• #6

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amdish

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dial tone generation integrated circuits

dial tone generator

 

• Aug 18, 2004

• #7

fireplus

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made in chinese wire tone generator

hi,

i assume that you able to generate the tone but all your problem is how to modulate the signal on the telephone line , simply you can use isolation transformer(600:600) to modulate the audio signal to the telephone line.

bye

Fire in the Wire :sm2:

 

• Aug 19, 2004

• #8

sokrat

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romania dial tone empedance

Hi all

I think you device is detect the line status(on hook or off hook)first and then send the dial tone and note your device will not send dial tone if see the line status is on hook
So you make fake off hook status

Note:

On hook the voltage on line is around 48 dcv and off hook will be less than 21dcv depend on the telephone impedance

S 8O KRAT

 

• Aug 24, 2004

• #9

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cherrytart

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dial tone detect circuit

If your device simply detects the line voltage, you might be able to easily fake this with a jumper somewhere inside the device, with a little reverse engineering.

There would be some circuit monitoring the voltage between the tip and ring, likely a very simple circuit,easy to trace and reverse engineer. Optocouplers are common for this purpose, but its not a certainty. Sometimes the voltage is rectified, in case tip and ring are reversed.

If the device is powered by the telephone line, there will be a power supply circuit to figure out (unless the device is very simple, that is, has no integrated circuits) but with luck it will be a simple 3 terminal regulator.

 

• Sep 3, 2004

• #10

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SPATAN

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telephone dial tone generator

You can use PSOC microcontroller.Because it has dtmf module.

 

• Sep 4, 2004

• #11

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seven_segment

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phone line generator schematics

You don't necessarily need a DTMF module, the same thing could surely be done through a DAC, R2R ladder or even PWM with filtering.

 

• Sep 12, 2004

• #12

UroBoros

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psoc+dtmf+generator

fireplus said:

hi,

i assume that you able to generate the tone but all your problem is how to modulate the signal on the telephone line , simply you can use isolation transformer(600:600) to modulate the audio signal to the telephone line.

bye

Fire in the Wire :sm2:

Click to expand...

Hai
Can you provide some more details as how can I inject a dial tone or some other audio into the telephone line? For example, I want to do a Answering mechine,after the ringing signal for a particular period of time the controller will pull the line in off hook mode,then I want to inject the audio .That is my purpose. 600:600? Can you provide some more details of the output stage of that amplifier?
Picstudent

 

• Sep 12, 2004

• #13

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C-Man

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600:600 isolation circuit optocoupler telephone

Take a look at the attached picture, this is a simple telephone interface that I am using. You can only inject simple tones (not voice) using this circuit.

best regards

 

• Sep 12, 2004

• #14

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mhamed

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faking a dialtone

for connecting any circuit to telephone line you should use tel transformer(or hybrid transformer which is a transformer 1:1 with 600 ohm impadance 600ohm is impadance of tel line)trans isolate to circuit from DC voltage. I recommend not use capacitors because it is so damager.