| 摘要 |
A device for monitoring operating conditions of an RF transmitter, including the RF power output thereof, and the reflected voltage wave on a transmission line therefor, and for promptly switching the transmitter off whenever a faulty condition is detected. The device includes two voltage comparators that receive voltage signals representative of transmitter power output and the magnitude of the reflected voltage wave on an associated transmission line, and which generate an output signal whenever a respective voltage signal varies a predetermined amount from a preset reference voltage level. The two voltage comparators are activated by a relay operated by the carrier wave of the transmitter so that the comparators function only when the transmitter is operating. The output signals from the two comparators are transmitted together with any other signals indicating a faulty condition, to a NAND gate which outputs an alarm signal whenever at least one fault signal is received. The alarm signal is then processed to switch off the transmitter and, if desired, to simultaneously switch on an alternate backup transmitter. A third comparator associated with the amplifier circuit for the meter that indicates the transmitter power output is used to provide a transmitter-on condition indication once the transmitter reaches a power level of 2% of its output power after being switched on.
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