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CompTIA Network+ (N10-009)Network ImplementationMedium

A technician is installing a PTZ security camera that requires 25.5W of power delivered over Ethernet at the powered device. Which PoE standard must the switch support to meet this requirement?

  1. APassive 24V PoE injector only
  2. B802.3af (PoE)
  3. C802.3at (PoE+)
  4. D802.3bt Type 3 only for lighting
Show answer & explanation

Correct answer: C. 802.3at (PoE+)

802.3at, also known as PoE+, supplies up to 30W at the power sourcing equipment, which delivers approximately 25.5W at the powered device after accounting for cable loss, making it suitable for higher-power devices like PTZ cameras.

Why the other options are wrong

  • A. Passive PoE injectors are non-standard and do not guarantee safe negotiated power delivery.
  • B. 802.3af (PoE) only provides up to 15.4W at the source, about 12.95W at the device, insufficient for this camera.
  • D. 802.3bt is a real standard for higher power (up to 60/100W) but is unnecessary overkill and 'Type 3 only for lighting' misrepresents its general use.

PoE Standards (802.3af/at/bt)

IEEE standards defining how much power can be delivered over Ethernet cabling to powered devices.

  • 802.3af (PoE): up to 15.4W at source / 12.95W at device
  • 802.3at (PoE+): up to 30W at source / 25.5W at device
  • 802.3bt (PoE++): up to 60W or 100W depending on type

Memory trick: 'af < at < bt' — more letters, more watts.

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