Which term refers to a system where a central receiver requests data from instruments over a single channel?

Which term refers to a system where a central receiver requests data from instruments over a single channel?

• A. Duplexing
• B. Polling
• C. Scanning
• D. Tone-frequency multiplexing

Answer: (B)

Polling is the method where a central receiver asks data from each instrument on a single shared channel, controlling who talks and when. The master probes each device in turn, waits for its response, then moves to the next device, so all data shares one line without collisions. This master-slave arrangement is ideal for orderly data collection from multiple sensors over one channel. Duplet-style duplexing implies simultaneous two-way communication, which isn’t about one device being asked at a time. Scanning refers to repeatedly checking devices, often in a loop, but the explicit master-initiated request-and-response pattern that isolates access to one device at a time is characteristic of polling. Tone-frequency multiplexing uses distinct tones to carry multiple signals on a single channel rather than a control-and-response polling scheme.

Polling is the method where a central receiver asks data from each instrument on a single shared channel, controlling who talks and when. The master probes each device in turn, waits for its response, then moves to the next device, so all data shares one line without collisions. This master-slave arrangement is ideal for orderly data collection from multiple sensors over one channel. Duplet-style duplexing implies simultaneous two-way communication, which isn’t about one device being asked at a time. Scanning refers to repeatedly checking devices, often in a loop, but the explicit master-initiated request-and-response pattern that isolates access to one device at a time is characteristic of polling. Tone-frequency multiplexing uses distinct tones to carry multiple signals on a single channel rather than a control-and-response polling scheme.