| 摘要 |
<p>The modulator is for a phonocardiograph and modulates the rectified, amplified microphone signal onto a carrier, and has an output connected to a recorder. One input of a flip-flop is connected to the output of a free-running multivibrator, and a symmetrical input of a balanced modulator for the carrier is connected to a symmetrical output of the flip-flop. Outputs of a symmetrical signal detector are connected to the symmetrical input of the balanced modulator, to whose asymmetrical output is connected an output capacitor, which forms, with the modulator output impedance, a low-pass filter. The modulator contains no transformer, and its parameters are unaltered with temp. and time. The circuit gives a wide dynamic range and good signal to noise ratio.</p> |
