In a monostatic sensor, where are the transmitter/emitter and receiver located?

• A. In separate units at opposite ends
• B. In the same unit at the same end of the detection zone
• C. One is external, one internal
• D. Both on the outer wall

Answer: (B)

In a monostatic sensor, the transmitter and receiver are housed in the same unit, located at the same end of the detection zone. This means the device both emits the signal and listens for its reflection from the same physical location. Keeping the TX and RX together simplifies installation and alignment, leads to a compact design, and is typical for many residential security sensors such as PIR or microwave units. If the transmitter and receiver were placed in separate units at opposite ends (or in different locations), that would describe a bistatic arrangement, which is not the monostatic setup.