Automatic Call Recorder

Automatic Call Recorder

This project is an improved version of the previous Automatic Call Recorder (Project # 20510). The improvements include the addition of a Tray Icon for easy access when in hide mode, Audio Transformer for improved sound quality, replaced ICs for easy assembly, and removed Trimmer so there is no adjustment required.

The program still has all the features the original except for a few minor changes that caused the program to hang up when there were numerous call files. Added renaming routine in the Audio form to rename all files, not renamed by the user, to keep them in order.


1. Can be set for Manual or Automatic recording for Telephone and/or Microphone.

A. Manual Mode

1. Clicking the ON/OFF Button Starts and Stops recording of the Telephone or Microphone connected to the adaptor. (Microphone button on adaptor not used.)

B. Automatic Mode

1. Automatically starts and stops recording when Telephone is answered and hung up respectively.

2. If microphone is connected to the adaptor, Microphone button used to starts and stop recording.

3. If Answering Machine answers, the recorder will also record the Message.

2. Creates a separate wav file with date and time for each Phone Call.

A. When a call is recorded from the Telephone, the file has a prefix of “Phone”.

B. When a call is recorded from the Microphone, the file has a prefix of “Microphone”.

C. When using Manual record the file has a prefix of “Manual”.

3. Options to Delete or Rename the files when Telephone is hung up.

A. Selecting the Check Boxes will allow prompts for Deleting and/or Renaming files at end of call.

1. In manual mode, prompt stays open until user make selection.

2. In automatic mode, selection must be made in 15 seconds or prompt screen closes and saves call.

B. When renaming the files, your file name replaces the prefix. The Date and Time stay the same.

4. Hide and Show screen option.

A. When in Show mode, Recorder screen appears on Monitor all the time.

B. When in Hide mode, an icon appears or disappears on the task bar when Telephone is answered or hung up respectively.

C. When in Hide mode, an icon appears or disappears on the task bar when Microphone button is pushed on or off respectively.

NOTE: Screen must be initially hidden with the Hide Screen button after selecting hide option.

5. Several user friendly screens for easy operation. All screens have their own Help Files.

A. Main Screen

1. Recording ON/OFF button to Start/Stop recording in Manual Mode.

2. Selection of Automatic/Manuals Mode.

3. Selection to Hide/Show screen.

4. Selection to prompt for deleting file at call time.

5. Selection to prompt for renaming file at call time.

6. Navigation to other screens.

B. Show/Play Files Button opens the file maintenance screen.

1. Rename, Delete and Play files. When renaming the files, what you type as the new name replaces the prefix. The Date, Time stay the same.

2. Navigate through all directories on your computer.

C. “Hide Recorder” button initially hides the Main Screen in automatic mode

D. “Close Recorder” button completely shuts down the recorder.

E. “Screen Help” button opens help screen for the Main Screen.

F. “…” button opens screen to select where you want the call files saved.


The circuit consists of four main sections.

The first section of the circuit consists of the phone ON / OFF hook sensing circuit. The phone connects to the 2 6x4 modular jacks. The incoming phone line connects to one jack and the phone connects to the other. The circuit is polarity sensitive so I used 4 diodes connected to the input jacks to insure the polarity is always correct. The On/Off hook sensing circuit also includes 4 Resistors, 1 Capacitor and 2 Transistors. The 2 Transistors are turned on or off when the phone comes off hook or goes on hook respectively.

The second part of the circuit consists of the controlling circuit for the Serial / USB Port which tells the program when to start and stop the recording. When the phone comes off hook the Transistors send a +v single to the DB9 connector connected to the Computer. The Program reads this as a pin change event and activates the start recording routine. When the phone goes on hook the Transistors sends a –v single which the Program reads as another pin change event. The Program stops the recording routine and saves the file.

The third part of the circuit consists of the sound circuit. An Audio Transformer is connected to the phone lines through a resister and capacitor. The other side of the Audio Transformer is connected to the 3.5mm Audio Jacks. The audio jack is connected to the sound card in the Computer

The forth part of the circuit consists of the supply voltage circuit. I wanted to make this adapter self-contained meaning I would have to use the voltage from the Serial Port which is approximately 12 volts. I also wanted to use a Serial to USB adapter so the user could have a choice between Serial and USB to connect the adapter to the computer. The USB voltage is approximately 5v. Switching from Serial to USB or vice versa caused the sensing circuit problems. The sensing circuit depends on this voltage to be stable. This was accomplished by using a 3 Volt Zener Diode as a voltage regulator obtaining a stable 3 volts needed to power the circuit.