| 摘要 |
1,072,312. Signal generators; transistor oscillator circuits. MARCONI INSTRUMENTS Ltd. Oct. 28, 1965 [Jan. 7, 1965], No. 781/65. Headings H3T and H4L. [Also in Division G3] The frequency range covered by a signal generator is divided into a number of subranges, each of which is covered by an independent transistor oscillator. In use, all the oscillators are energized but oscillation is prevented, except in the one for the sub-range required, by a diode or thermistor 7 paralleled across each tank coil 3 and rendered conductive by forward bias applied through a resistor 11. This bias is countered in the operative oscillator by closure of its selector switch 10, whereby back bias is applied through an adjustable resistor 9, so that its diode 7 becomes non- conductive. In another embodiment, part of the output of the oscillator is rectified and the voltage developed across a resistor (13), Fig. 2 (not shown), is applied to the base of a transistor (99) which is connected, together with a reference voltage source (12), in place of the resistor 9. In this way, by variation of the resistance of the transistor (99), the output of the oscillator is automatically kept substantially constant. |
