For safety reasons, the speakerphone in the vehicle must be factory made. But at home, you can experiment with homemade systems. The sound quality will be much higher than with the hands-free speaker built into the phone.
Instructions
Step 1
Get any bluetooth headset. It may be the cheapest, since ergonomics does not matter in this case. You can also use an old appliance that you no longer use for its intended purpose.
Step 2
Open the headset. First of all, unsolder the battery, having previously memorized or sketched in what polarity it was connected. Drain quickly to avoid overheating the battery.
Step 3
Find a sound emitter. Unsolder it, and then connect a resistor of about 100 ohms instead.
Step 4
Get a headphone jack that accepts a 3.5mm stereo plug. Solder a jumper wire between the left and right channel pins. Between the jumper and one of the terminals of the resistor that you installed in the headset instead of the sound emitter, connect a capacitor with a capacity of about 0.1 μF. Connect the other end of this resistor directly to the common terminal of the socket.
Step 5
Solder the battery back, observing the polarity. Turn on the headset and pair it with your phone.
Step 6
Take active computer speakers. Set the volume in them to minimum, then plug into the jack you installed in the headset. Extend the cable fully so that the headset microphone is away from the speakers. Turn on their power.
Step 7
From your telephone, call the automatic information service number. This call is free when you are in your home region. On the speakers, gradually turn up the volume until the echo from the acoustic feedback appears. Decrease the volume slightly so that the echo disappears.
Step 8
Make a small notch in the headset body to lead the wire to the added jack. Close the headset, and then make sure that it does not become ineffective after that. Now you can use your home-made hands-free system, remembering to periodically charge the headset battery with the included charger.
