/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: 7,995

Rating: (2.88, votes 3964)


Date: 02-03-2010

Lokalna verzija ove stranice: Snimač telefonskih razgovora


Bookmark and Share Comments (43)

comment [23]

how I connected transformer output to PCs sound card can be seen in schematics (click on the red download button above), and you can read about the software in the text above. The PIC sends commands to software via UART and the software starts/stops recording.
IP: n/a

comment [22]

hi!can you tell how you have connected transformer output to pc?also tell how the software works?please reply soon.

comment [21]

can u please provide me the phone recording software for windows.....

comment [20]

If you don't want to use PL2303 USB converter, you can use MAX232 to connect PIC to PC's Serial COM port. The TX pin from PIC is connected to MAX232 TTL input. See schematics for MAX232 on internet to see what you need to build.
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comment [19]

It's Great. It can work with serial port? How? I build it, but didn't work. Please help me to my E-mail address. A lot of thanks.

comment [18]

MCLRE=on, EXTERNAL XT crystal, CP=nebitno, WDT=off... ne znam sta jos ti treba.
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comment [17]

Postovani, dali mi mozete reci kako da postavim parametre prilikom programiranja pic-a 16F84A sa programatorom allpic... i programom 106.D Zasad sam programirao samo 12f629 za IR light dimmer Zahvaljujem unapred vlado.georgiev@mt.net.mk

comment [16]

Dear Trex I like your project can you send me the source code I who'd like to play with Regards, Moshe
IP: n/a

comment [15]

The project is great and interesting.Can you send me the source code for windows application.Thanks very much!
IP: n/a

comment [14]

Check your e-mail...
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