What is the function of an SPDT switch?
The correct answer is C: A single circuit is switched between one of two other circuits. The function of an SPDT (Single-Pole Double-Throw) switch is to switch a single circuit between one of two other circuits. An SPDT switch has one input (pole) that can be connected to either of two outputs (throws).
SPDT switches have three terminals: one common terminal (pole) and two output terminals (throws). The switch connects the common terminal to one of the two output terminals. This allows you to switch a single circuit between two different paths. SPDT switches are commonly used for selecting between two antennas, switching between two power sources, or routing signals to different destinations. They're essential for circuit control and signal routing in radio equipment.
Exam Tip
SPDT = One input, two outputs. Remember: SPDT (Single-Pole Double-Throw) switches a single circuit between one of two other circuits - one pole, two throws.
Memory Aid
"**S**PDT = **S**ingle **P**ole, **D**ouble **T**hrow (think 'SPDT = 1 pole, 2 throws')"
Real-World Application
You're setting up your station with two antennas. You use an SPDT switch to select between them. The switch has one input (from your transceiver) and two outputs (one to each antenna). You can switch between the two antennas, but only one is connected at a time. This is the function of an SPDT switch.
Key Concepts
Why Other Options Are Wrong
Option A: Incorrect. A single circuit opened or closed describes an SPST (Single-Pole Single-Throw) switch, not an SPDT. SPDT switches have two output positions, not just on/off.
Option B: Incorrect. Two circuits opened or closed describes a DPST (Double-Pole Single-Throw) switch, not an SPDT. SPDT has one pole, not two.
Option D: Incorrect. Two circuits each switched between one of two other circuits describes a DPDT (Double-Pole Double-Throw) switch, not an SPDT. SPDT has one pole, not two.
题目解析
The correct answer is C: A single circuit is switched between one of two other circuits. The function of an SPDT (Single-Pole Double-Throw) switch is to switch a single circuit between one of two other circuits. An SPDT switch has one input (pole) that can be connected to either of two outputs (throws). SPDT switches have three terminals: one common terminal (pole) and two output terminals (throws). The switch connects the common terminal to one of the two output terminals. This allows you to switch a single circuit between two different paths. SPDT switches are commonly used for selecting between two antennas, switching between two power sources, or routing signals to different destinations. They're essential for circuit control and signal routing in radio equipment.
考试技巧
SPDT = One input, two outputs. Remember: SPDT (Single-Pole Double-Throw) switches a single circuit between one of two other circuits - one pole, two throws.
记忆口诀
**S**PDT = **S**ingle **P**ole, **D**ouble **T**hrow (think 'SPDT = 1 pole, 2 throws')
实际应用示例
You're setting up your station with two antennas. You use an SPDT switch to select between them. The switch has one input (from your transceiver) and two outputs (one to each antenna). You can switch between the two antennas, but only one is connected at a time. This is the function of an SPDT switch.
错误选项分析
Option A: Incorrect. A single circuit opened or closed describes an SPST (Single-Pole Single-Throw) switch, not an SPDT. SPDT switches have two output positions, not just on/off. Option B: Incorrect. Two circuits opened or closed describes a DPST (Double-Pole Single-Throw) switch, not an SPDT. SPDT has one pole, not two. Option D: Incorrect. Two circuits each switched between one of two other circuits describes a DPDT (Double-Pole Double-Throw) switch, not an SPDT. SPDT has one pole, not two.
知识点
SPDT switch, Single-Pole Double-Throw, Switch function, Circuit switching
Verified Content
Question from official FCC Technician Class question pool. Explanation reviewed by licensed amateur radio operators.