| 摘要 |
<p>A two wire repeater system for telephone communication includes an additional amplifier loop responsive to frequencies outside the audio-frequency bandwidth. Two way amplification of audio frequencies is provided by two amplifier loops (2, 4, 5, 6, 8) and (8, 10, 11, 12, 2) coupled over branches consisting of four gates. Each loop has a bandpass filter (4) operating in the range 300 Hz to 3400 Hz, distortion correction stage (5, 11) and amplifier (6, 12). The gates ensure isolation between the audio amplifier loops. Balancing stages (3, 7) are coupled to each branch gating stage. Frequencies outside of the audio range are transmitted over a low band pass filter (13) and amplifier (14) and as such allow the transmission of call and tone signals. e.g. typically 16 Hz signals.</p> |
