| 摘要 |
It is known for the heater of a television camera recording tube to be supplied from a constant-current source, in order that the tube receives the correct heater power irrespective of the lead length and the lead resistance. The supply voltage of such current sources is in general much higher than the permissible heater voltage so that, if this voltage is applied to the tube heater in the case of a defect in the current source, the tube is destroyed. The protection circuit according to the invention against an overload of the tube heater is for a fuse (SI) to be connected in the supply lead to the current source. A switch (TH) is connected in series with said fuse, which switch carries a current, in the closed switch position, which causes the fuse to trigger and which is controlled by a voltage monitoring device (Z2, R12, TS4) which is connected to the cathode heater (H) and closes the switch (TH) when the voltage on the cathode heater exceeds a predetermined value. The main field of application of the invention is television recording tubes. <IMAGE>
|
