Comtech EF Data HPCST-5000 - Manual (Page 121)

High-Power TWTA Satellite Terminals TWT Amplifiers
Rev. 1 4–3
4.1.2.2 Heater Standby
Heater Standby is enabled when the Heater Standby control line is set low. When prime
power is first turned on, full heater voltage is applied during the Heater Delay mode. At
the end of the Heater Delay mode, the heater voltage is reduced if the high voltage is
OFF, and Heater Standby is enabled.
The heater voltage reduction feature enhances tube life when the amplifier is the backup
unit in a redundant configuration. In this mode, the TWT is ready for high voltage to be
applied. Heater voltage returns to normal when High Voltage ON is enabled, or Heater
Standby is disabled (set high).
4.1.2.3 Standby
In Standby mode, the TWT is ready for high voltage to be applied. The Timer Complete
status line is active (low), and the High Voltage ON status line is not active (high).
4.1.2.4 High Voltage ON
When High Voltage is ON (applied to the TWT), RF input signals are amplified, and the
High Voltage ON line is active (low). If the High Voltage ON control line is activated
(set low) before the Heater Delay is complete, high voltage remains off until the delay is
complete.