| 摘要 |
784,444. Substation equipment. PLESSEY CO., Ltd. June 25, 1956 [June 23, 1955], No. 18191/55. Class 40 (4). [Also in Group XL (c)] A substation bell is rung by 17 cycle current derived from a transistor oscillator TS1, Fig. 2, whose output feeds a push-pull class B transistor amplifier TS2, TS3 whose output is taken off transformer TR2 to ring the bell. The switch SW may be replaced by a further transistor TS4, Fig. 3, which is caused to become conducting by the application of high frequency alternating potential to its base. The circuit is suitable for use in mines. |
