UPSC Prelims 2022 Q36: Short-Range Devices – CCTV, RFID, WLAN
Consider the following communication technologies:
1. Closed-circuit Television
2. Radio Frequency Identification
3. Wireless Local Area Network
Which of the above are considered Short-Range devices/technologies?
- 1 and 2 only
- 2 and 3 only
- 1 and 3 only
- 1, 2 and 3
Answer: (d) 1, 2 and 3
Statement-wise explanation
- 1: correct — Wireless CCTV cameras send video over low-power radio links to a nearby recorder or monitor, so they work only within a building or site. ETSI, the European telecom standards body, lists CCTV among the uses of Short Range Devices (SRDs). The signal is also 'closed': it goes to a fixed set of screens and is never broadcast.
- 2: correct — In Radio Frequency Identification (RFID), a reader picks up a tag from a few centimetres (passive tags on cards and goods) to a few metres (UHF tags such as FASTag at toll lanes). RFID is one of the standard SRD uses in European SRD rules (ECC Recommendation 70-03) and in ETSI standards. Reading a tag needs only very low power.
- 3: correct — A Wireless Local Area Network (Wi-Fi) is 'local' by definition. It covers tens of metres indoors using low-power transmitters in licence-exempt bands. In October 2018, India's Department of Telecommunications delicensed 605 MHz in the 5 GHz band for low-power wireless access systems, including radio LANs. Licence exemption for low-power use is the standard regulatory sign of a short-range device.
How to eliminate
Option logic does not help much here, because each of the three pairs leaves out exactly one technology. You can still get there from basic knowledge. WLAN has 'Local' in its name, so it is short-range. RFID tags are read only at a gate, a shop counter or a toll lane, so it is short-range. That leaves CCTV, the doubtful one, and the question is about communication technologies. A closed-circuit system sends its signal over a short link to a few fixed screens, wired or by low-power radio, and never broadcasts it. All three share the same defining features: low power, limited range and a local link. The fact to remember is that ETSI's list of Short Range Device uses includes alarms, CCTV, RFID, wireless LANs, cordless audio, remote controls and telemetry.
Know more
Short Range Devices (SRDs) are radio transmitters with so little power that they barely interfere with other radio services. Under the European framework (ECC Recommendation 70-03, ETSI standards), they usually transmit at about 25–100 mW or less and reach a few metres to a few hundred metres. Because the interference risk is low, regulators let people use them without an individual licence, but only in set frequency bands and under power limits.
How India regulates them: The Department of Telecommunications' Wireless Planning & Coordination (WPC) Wing delicenses specific bands for low-power equipment by gazette notification. The equipment still needs Equipment Type Approval. Examples:
| Band | Typical use |
|---|---|
| 2.4–2.4835 GHz | Wi-Fi, Bluetooth |
| 5 GHz (605 MHz delicensed, 2018) | Wi-Fi / radio LANs |
| Lower 6 GHz, 5925–6425 MHz (2026) | Next-generation Wi-Fi, indoor low-power |
| 865–867 MHz | UHF RFID (e.g. FASTag) |
Common SRD families:
| Family | Examples | Typical range |
|---|---|---|
| Identification | RFID, NFC | cm to a few metres |
| Data networks | Wi-Fi (WLAN), Bluetooth, Zigbee | metres to ~100 m |
| Security | Alarms, wireless CCTV, motion sensors | within a building or site |
| Control | Remote keys, garage openers, model controls | tens of metres |
| Audio | Wireless microphones, earphones | tens of metres |
| Vehicle | Short-range radar (76–77 GHz) | ~hundreds of metres |
How these differ from long-range systems: Mobile networks (4G/5G), broadcast TV and satellite links use licensed spectrum, which is auctioned or assigned by the government. They have far higher power and cover kilometres or even continents. SRDs share unlicensed spectrum on a 'no interference, no protection' basis. TRAI makes recommendations on delicensing, and DoT decides.
NCERT Concepts to Revise
- Electromagnetic spectrum: RFID, Wi-Fi and wireless camera links all use radio waves. Where they sit in the spectrum shows why frequency and power limit range.
- Telecom Regulatory Authority of India: TRAI recommends which spectrum bands DoT should delicense. That decides where low-power wireless devices may run without a licence.