/Projects/Phone recorder

How many times have you wished that you recorder your recent telephone conversation? I have, many many times. So I finally decided to make this happen by using PC and a piece of hardware (powered from USB) to record audio from phone line to MP3 format. I wanted this thing to work automatically, to start recording when any of phones in house is picked-up (line occupied) and stop recording when all phones are hung-up (line free).

UPDATE: The .RAR file is now updated. So if you have seen the "Output mp3 directory is not valid..." information upon application start, just edit the "opcije.ini" file and adjust the mp3 output directory.

[I'm on Hack-A-Day and also on HackedGadgets :-)]

Update: Source code is available for download [here].

You can download the project files (schematics, source code, windows app) by clicking on the red download button at the end of this article.


How does it work?
The hardware-part consists of:
- audio pickup circuit
- phone line status monitor
- microcontroller to send the phone-line state to PC using USB (serial<->usb)




The software:
- receiving the phone-line state via USB and managing the recording to WAV
- after conversation is finished, converts WAV to MP3 using Lame library


Phone line status monitor circuit
This circuit is basically measuring voltage on the phone-line, which is is above 15 Volts (around 50) when on-hook. When any of the phones is picked-up the voltage drops below 15 Volts. This property is used to detect whether the phone line is in-use or not. The circuit is actually taken from this address and altered a bit.

Audio pickup from telephone line
In this simple part a transformer from an old PC modem i used. There are also 2x1N4148 diodes to limit the output voltage of the transformer to ~0.6V, a resistor and a capacitor. The important part is this capacitor which ensures that phone-line is never occupied by the circuit.

Microcontroller to send data to PC
Microcontroller is checking the phone line status every 0.2 seconds with a help of monitor circuit above. If the optocoupler is "closed" for more than 0.15 seconds it means that the phone line is occupied and it starts to send letter "R" (Rec) to PC application. In other case it sends "S" (Stop). This data is received by the PC where the application starts audio recording (R) or stops (S). Since the microcontroller uses serial communication to send the data, PL-2303 circuit is used to translate those signals to USB. (An entire PCB converter is used in this application, as it can be seen in the picture.) Much better way of doing this is would be with V-USB library (see these simple projects). That way we could use only one Atmel chip instead of these two (PIC + PL-2303).



Author (sent by): Trax

Download counter: 8,112

Rating: (2.88, votes 4258)


Date: 02-03-2010

Lokalna verzija ove stranice: Snimač telefonskih razgovora


Bookmark and Share Comments (43)

comment [13]

Good evening!! That's a great project!!! Can you let me see your code in delphi??? I'll appreciate it. Thanks

comment [12]

It is all in the description. Read it: http://www.elektronika.ba/746/phone-recorder/
IP: n/a

comment [11]

Could you please tell me what does PIC 16F84 do? what are the functionality of this ID? and I got to know that this IC is a programmable IC. In your project, are we doing any programming for this IC. regards, Ravi

comment [10]

Sorry, I have been busy. I will try tonight!
IP: n/a

comment [9]

I will send it later today. Ok. I'm waiting. Please send it to my email address. Many thanks.

comment [8]

I will send it later today.
IP: n/a

comment [7]

Hi... I interested to get the Delphi 7 source code of call recorder application. Could you send it to my email? Thanks.

comment [6]

Ok, probacu...Hvala!
IP: n/a

comment [5]

Potreban ti je samo grecov spoji koji spojis na tel. liniju i nakon njega stabilizator napona i to je to. Problem je sto ne smijes uzimati sa tel. linije vise od nekih 20-tak mA! U tom slucaju telecom to registruje i iskljuci te jer misli da imas neki kvar na aparatu.
IP: n/a

comment [4]

Trebam i ja raditi neki slican uredjaj, ali nema vezu sa racunarom a treba da se napaja sa 5v iz linije. Dali moze neko objasnjnje ili samo kako bi se moglo izvesti napajanje?
IP: n/a

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