Welcome to Comrex Corporation.
Skip to: Content, Main Navigation, or Section Navigation.
Support

Tech Notes

Connecting a Comrex TCB-1 to a PC Sound Card

The Comrex TCB-1 Manual Coupler allows you to record audio from, or send audio to a telephone line. When properly connected, the audio should be as hum and noise free as a regular call on that line. Since this coupler was originally designed for radio broadcasting applications, some additional instructions are necessary for use with a PC sound card.

The first step is to make or buy the correct cable to complete the audio connection between the TCB-1 and the sound card. We suggest a quick trip to Radio Shack for these two items:

  • 42-2433 1/4" mono plug to 1/8" mono plug cable
  • 274-374 1/8" mono jack to 1/8" stereo plug adapter

Put the 1/8" plug on the cable into the 1/8" jack on the adapter. Plug the 1/4" plug into the TCB-1. If you are going to record from the telephone line, plug the 1/8" adapter into the microphone input of the sound card. If you are going to send audio from the sound card to the line, plug the 1/8" adapter into the line output of the sound card.

With the telephone line plugged into the "LINE" jack on the TCB-1, and a telephone set plugged into the "TEL SET" jack, follow the "Operation" instructions in the TCB-1 manual to place or receive a call. You will need to set the proper audio levels using your PC card’s software. Computers running Windows 95, 98 or NT usually have a sound card icon at the lower right side of the screen. Clicking on this will give access to the volume controls for your card.

If you are receiving audio, use the microphone level control on the PC screen. We can’t give instructions as to how to set it, as it will depend on the software you are using to record that audio.

If you are sending audio, however, you do need to be careful not to send too high a level into the telephone line. As a starting point, place or receive a telephone call, and adjust the "volume" or "line out" control on the PC screen for a normal listening level at the other end of the call.

As the manual explains, the TCB-1 is a coupler, and you can either send or receive audio with it. You cannot do both at once! That would require a telephone hybrid, which equalizes the levels between sending (loud) and receiving (soft).