| 摘要 |
A power amplifier for use in uni-directional telephone line signal amplification requirements on voice and data grade circuits includes a balanced input transformer and associated differential line transient protection circuit and line matching network, a balanced differential voltage feedback amplifier circuit with externally interchangeable, balanced, passive, terminated attenuators in the voltage feedback path for varying the amplification factor of the signal amplifying circuit, a balanced-to-unbalanced common mode rejection circuit, low and high cut frequency filters, and a balanced output transformer with associated output line matching and circuit protection components. The interchangeable attenuators are calibrated and marked in terms of overall power amplification resulting from their individual and specific use in the circuit.
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