| 摘要 |
<p>Appts. testing the hearing of a patient uses an audio frequency generator (10) connected to an amplifier (11) for signals passed to earphones (12) for the patient. Signals of different frequencies and at different levels can be generated to reduce crackling or other noises from the switches (19,20), resistive devices are incorporated, which can be f.e.t.s. These are controlled by RC members (15,16). Thus the member (15) connected to the controller (13) for the frequency control switch (19) allows it to be operated slowly as it changes from a low setting to a high setting. The level control switch (20) is operated similarly, by a controller (14) with an earth connection, which operates in the opposite direction to the first controller (13).</p> |
