Here's a professional English introduction to IEEE 802.3at (PoE+):
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### **IEEE 802.3at (PoE+) Standard Overview**
**Official Designation:** *IEEE 802.3at-2009*
**Common Name:** *Power over Ethernet Plus (PoE+)*
#### **1. Key Specifications**
- **Power Delivery:**
- **30.8W max** per port (at power source)
- **25.5W guaranteed** at powered device (PD)
- **Voltage Range:** 50-57V DC
- **Current:** Up to 600mA (per power pair)
- **Cable Requirements:** CAT5e or better (4-pair power delivery recommended)
#### **2. Technical Advancements over 802.3af (PoE)**
✔ **2x Power Increase** (vs 15.4W in 802.3af)
✔ **4-Pair Power Option** (Alternative B wiring)
✔ **Enhanced Classification** (5 power classes vs 3 in 802.3af)
✔ **Layer 2 Communication** (LLDP power negotiation)
#### **3. Power Classification**
| Class | PSE Output | PD Input | Usage Example |
|-------|------------|----------|---------------|
| 0 | 15.4W | 0.44-12.95W | Basic IP phones |
| 1 | 4.0W | 0.44-3.84W | Sensors |
| 2 | 7.0W | 3.84-6.49W | Basic cameras |
| 3 | 15.4W | 6.49-12.95W | PTZ cameras |
| 4 | 30.8W | 12.95-25.5W | WiFi-6 APs, videophones |
#### **4. Typical Applications**
- **Enterprise WiFi Access Points** (802.11ac/ax)
- **Pan-Tilt-Zoom (PTZ) IP Cameras**
- **Videoconferencing Systems**
- **Digital Signage Displays**
- **Thin Client Computers**
#### **5. Compliance Testing**
- **PSE (Power Sourcing Equipment):** Must deliver minimum 30W per port
- **PD (Powered Device):** Must accept 25.5W minimum
- **Voltage Tolerance:** ±3% regulation required
- **Safety Standards:** UL 60950-1, EN 60950-1
#### **6. Comparison with Other Standards**
| Feature | 802.3af (PoE) | 802.3at (PoE+) | 802.3bt (PoE++) |
|---------|---------------|----------------|----------------|
| Max Power | 15.4W | 30.8W | 60W/90W |
| Voltage | 44-57V | 50-57V | 50-57V |
| Current | 350mA | 600mA | 960mA |
| Pairs Used | 2-pair | 2/4-pair | 4-pair |
#### **7. Installation Notes**
- **Cable Length:** Max 100m (328ft)
- **Power Loss:** ≤12% over 100m CAT5e
- **Heat Management:** Bundle ≤24 cables in conduit
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This version maintains technical accuracy while being accessible for:
- **Network engineers** (detailed specs)
- **Procurement teams** (comparison tables)
- **Installers** (practical notes)
Would you like me to focus on any specific aspect (e.g., testing procedures, market adoption statistics)?
