Which of the following can be used to enter a transceiver's operating frequency?

The ability to enter a transceiver's operating frequency is fundamentally centered around direct frequency entry methods. The keypad or VFO (Variable Frequency Oscillator) knob serves as two primary means to accomplish this. The keypad allows users to input specific frequencies directly by typing, while the VFO knob enables users to tune continuously through a range of frequencies until the desired one is reached. These methods are essential for quickly setting up a radio for communication on various frequencies.

In contrast, a CTCSS (Continuous Tone-Coded Squelch System) or DTMF (Dual-Tone Multi-Frequency) encoder does not function to set the operating frequency of the transceiver; instead, they serve different purposes such as enabling privacy codes or facilitating signaling for different functions in the radio. Automatic Frequency Control (AFC) is involved in stabilizing the frequency but does not allow direct entry of a frequency by the user. Thus, while these are important features, they do not fulfill the specific requirement of entering the transceiver's operating frequency.