🧠 1. What exactly is the TG400L?

The Yeastar TG400L is a 4G LTE VoIP gateway that connects mobile SIM networks (4G/3G/GSM) to VoIP/IP PBX systems.

👉 In simple terms:

TG400L = SIM card (mobile network) → converted into VoIP system

Unlike FXO gateways (TA series):

• TA = connects landlines (PSTN)
• TG = connects mobile networks (SIM-based)

---

🔄 2. Core Function (How it works)

Step-by-step:

1. Insert SIM cards into TG400L
2. Device connects to 4G LTE mobile network
3. Converts voice → SIP (VoIP packets)
4. Sends to IP PBX / VoIP server

👉 Calls work both ways:

• 📞 Mobile → VoIP users
• 📞 VoIP → mobile network

✔ This is called GSM/LTE to VoIP bridging

---

🔌 3. Hardware & SIM Capacity

📡 SIM / LTE Ports

• 4 × LTE ports (SIM slots)

👉 Meaning:

• Supports 4 simultaneous calls
• Each SIM = 1 channel

---

🌐 Network Interface

• 1 × 10/100 Mbps Ethernet port

👉 Connects to:

• Router / switch / PBX

---

📡 4. Mobile Network Features

Supports:

• 4G LTE
• 3G / GSM fallback

---

📞 VoLTE (Very Important)

• Supports VoLTE (Voice over LTE)

👉 Benefits:

• HD voice quality
• Faster call setup
• Better reliability than GSM

---

📞 5. VoIP & Protocol Support

Supported protocols:

• SIP (main VoIP protocol)
• IAX2

---

Transport & security:

• UDP / TCP
• TLS / SRTP (secure calls)

👉 Works with:

• Asterisk
• 3CX
• Yeastar PBX
• Most IP PBX systems

---

🔊 6. Voice & Audio Processing

Codecs:

• G.711, G.722, G.729, GSM, Speex

---

Voice optimization:

• Echo cancellation (G.168)
• Jitter buffering
• Packet loss handling

👉 Result:

• Stable and clear voice calls

---

📩 7. SMS & Messaging Features (Unique Feature)

📩 SMS capabilities:

• Send / receive SMS
• Bulk SMS campaigns

👉 Use cases:

• OTP messages
• Marketing campaigns
• Alerts / notifications

---

🔄 8. Key Business Functions

📞 Call routing

• Route calls based on:
  • SIM
  • Time
  • Prefix

---

📊 Call management

• Call detail records (CDR)
• Call duration limits
• Blacklist / whitelist

---

🔁 Failover / Backup

• If SIP trunk fails → use SIM network
• If internet fails → mobile fallback

👉 Very useful for business continuity

---

🔐 9. Network & Security Features

• Firewall
• VLAN support
• QoS (voice priority)
• OpenVPN
• DDNS

👉 Ensures:

• Secure and stable operation

---

⚙️ 10. Management & Configuration

Setup methods:

• Web-based GUI
• Remote provisioning
• API (SMS/USSD integration)

👉 Easy to deploy in enterprise environments

---

🔗 11. System Integration

The TG400L integrates with:

• 📞 IP PBX systems (Asterisk, 3CX, Yeastar)
• ☁️ Cloud VoIP platforms
• 📱 Mobile networks

---

Example:

• Office IP phones → call mobile numbers via SIM
• Customers call mobile number → routed to VoIP system

---

🏭 12. Real-World Use Cases

1. Call cost reduction

• Use local SIM cards for mobile calls
  👉 cheaper than VoIP termination

---

2. SMS marketing / alerts

• Bulk SMS campaigns
• OTP / notifications

---

3. Backup communication

• Internet down → still use mobile network

---

4. High mobile call traffic

• Call centers calling mobile numbers

---

⚖️ 13. TG400L vs TA410 (Important Difference)

👉 Simple idea:

• TG400L → mobile network gateway
• TA410 → landline gateway

---

⚠️ 14. Limitations

• Requires:
  • Active SIM cards
  • Good mobile signal
• Limited to 4 channels
• Not useful if:
  • You only use VoIP (no SIM needed)

---

🧠 Final Simple Explanation

The Yeastar TG400L is a 4-port LTE VoIP gateway that lets businesses connect mobile SIM networks to VoIP systems, enabling calls and SMS over mobile networks while integrating with IP telephony.

---

👍 When should you use it?

Choose TG400L if you need:

• To connect SIM/mobile network to IP PBX
• Reduce cost of mobile calls
• Send/receive SMS from VoIP system
• Backup communication via 4G