Which device commonly affects wireless networks?

• A. Blu-ray players
• B. External hard drives
• C. Cordless phones
• D. Incandescent light bulbs

Answer: (C)

Wireless networks share the airwaves, so any device that transmits in the same frequencies can cause interference and degrade performance. Cordless phones are a common source because many models operate in the 2.4 GHz ISM band, the same band Wi‑Fi uses. When a cordless phone transmits, its signal can collide with a Wi‑Fi channel, reducing throughput and causing drops, especially in crowded environments.

The other devices listed don’t typically emit in the same way or at the same frequencies. Blu-ray players use HDMI for data and don’t generate RF interference in the 2.4 GHz band. External hard drives communicate over USB or network connections but don’t broadcast on Wi‑Fi frequencies. Incandescent light bulbs don’t emit radio signals. So, cordless phones most commonly affect wireless networks. To mitigate, use the 5 GHz band if available, or choose less congested channels and separate the devices spatially.