Question T4A06
From subelement T4 - T4A
What signals are used in a computer-radio interface for digital mode operation?
Why is this correct?
Digital mode operation requires three essential signals between computer and radio: receive audio (radio sends received signals to computer for decoding), transmit audio (computer sends encoded data to radio for transmission), and transmitter keying (computer controls when radio transmits). The other options list unrelated functions - GPS/status data, antenna/power settings, or navigation protocols that aren't part of the basic computer-radio interface.
Memory tip
Remember the three-way handshake pattern: IN (receive audio from radio), OUT (transmit audio to radio), and CONTROL (keying signal). This same pattern appears in many amateur radio interfaces - always look for audio flow in both directions plus a control signal.
Learn more
In digital mode operation, your computer becomes the operator's voice and ears. Just as you need to hear incoming signals, speak outgoing messages, and press the PTT button, the computer needs receive audio to 'hear' decoded signals, transmit audio to 'speak' encoded data, and transmitter keying to 'press the PTT.' This interface enables modes like FT8, PSK31, and RTTY where precise timing and error-free data transmission exceed human capabilities.
Think about it
Why do you think the computer needs to control the transmitter keying rather than just sending continuous audio to the radio?