PoE (Power over Ethernet) injectors are devices that add power to an Ethernet cable so a network device can receive both data and power through one cable. They are commonly used for IP cameras, wireless access points, VoIP phones, and intercoms.

Here are the main types of PoE injectors:

By PoE Standard

1. Passive PoE Injectors

• Supply fixed voltage continuously on Ethernet pairs
• No negotiation with the powered device
• Usually 12V, 24V, or 48V
• Lower cost but risky if connected to non-compatible devices
• Common in older wireless equipment
• Typical use: Some wireless bridges and older outdoor APs

2. Active PoE Injectors (Standards-Based)

These follow IEEE PoE standards and safely negotiate power with the device.

• IEEE 802.3af (PoE)
  • Up to 15.4W output
  • About 12.95W usable at device
  • Used for:
    • • Basic IP cameras
      • VoIP phones
      • Small access points
• IEEE 802.3at (PoE+)
  • Up to 30W
  • Used for:
    • • PTZ cameras
      • Wi-Fi 6 access points
      • Video intercoms
• IEEE 802.3bt (PoE++ / 4P PoE)
  • Type 3: Up to 60W
  • Type 4: Up to 90–100W
  • Used for:
    • • Large displays
      • High-power PTZs
      • Digital signage
      • Thin clients
      • Smart lighting

By Voltage Output

• 24V Passive PoE: Common in older wireless networking gear.
• 48V PoE: Standard for IEEE PoE systems.
• 56V PoE++: Used for high-power devices.