15
•
Screen voltage regulator, with adjustable voltage and adjustable current limiting, for tube protection.
•
Overdrive protection and timer - based on detecting grid current, it initially gives visual warning and,
at higher level of overdrive, it cuts off the amplifier for 2 seconds. It ensures a clean signal, making
it virtually impossible to overdrive the DX-3
•
SWR detector and timer - switches the amplifier to bypass mode for about 3 seconds when high SWR
is detected. Adjustable SWR level. Factory adjusted to about 2.6: 1
•
EBS - the Electronic Bias Switch - senses the presence of RF input power and turns on the bias to start
transmission. Factory adjusted for about 0.5W. When the input power exceeds this limit, the plate
current starts flowing. When there is no speech, even for a very short time, the tube dissipation is cut
to a low value, as set by the pre-bias adjustment.
•
Interlocking, timer for filament warm-up
•
Relay control: ready relay, SWR relay, over-drive relay, antenna relay
•
QSK switching control
•
Display control: Ig2 measurement and display, SWR cut-off display, overdrive warning display,
READY display, FAULT display
•
Logic circuitry, low voltage supply to the various electronic circuits