Consider the following communication technologies :

Correct Option (d)

• Short-Range Devices (SRDs) are low-power radio transmitters designed to operate over a limited geographical area, typically without requiring an individual license. They are used for various applications including data transmission, control, and communication in localized environments.
• Closed-circuit Television (CCTV): Many modern wireless CCTV systems utilize short-range communication protocols such as Wi-Fi or Bluetooth for local video transmission within a building or confined area. These systems, when operating wirelessly over short distances, fall under the category of SRD technologies.
• Radio Frequency Identification (RFID): RFID technology inherently operates over short ranges, typically from a few centimeters to several meters. It uses radio waves to wirelessly transfer data from an RFID tag to a reader, making it a quintessential example of an SRD.
• Wireless Local Area Network (WLAN): Technologies like Wi-Fi, which form WLANs, primarily operate in unlicensed frequency bands (e.g., 2.4 GHz and 5 GHz) and are designed to provide network connectivity over a limited area such as a home, office, or public hotspot. Their localized coverage and relatively low transmission power classify them as SRDs.

Incorrect Options

• Options (a), (b), and (c) are incorrect because they exclude one or more of the listed communication technologies that are considered Short-Range Devices. As explained above, Closed-circuit Television (when wireless and local), Radio Frequency Identification, and Wireless Local Area Networks all function as short-range device technologies.