Overview
Crimson modem support uses PPP (Point‑to‑Point Protocol), enabling multiple logical connections over a single link, similar to Ethernet.
A single connection can support:
- TCP/IP downloads
- Web server access
- Serial port sharing
- TCP/IP protocol communications [modem-g3 | Word]
Typical Applications
- Send alarm emails via ISP connection
- Send SMS alerts via GSM modem
- Remote database updates and web access
- Remote SCADA access using Modbus TCP/IP [modem-g3 | Word]
Dial‑In Configuration
Driver
PPP and Modem Server
Key Settings
-
Connect Using
- Serial (Windows)
- Hayes modem
- GSM modem (CSD mode)
-
Activity Timeout
- Terminates connection after inactivity
-
Additional Init
- AT command string
-
SMS Support
- Enables messaging (requires Mail config)
-
Logon Username / Password
- Authentication (CHAP preferred, PAP fallback)
-
Local Address
- IP address of G3 interface
-
Remote Address / Mask
- Defines routing behavior [modem-g3 | Word]
Dial‑Out Configuration
Driver
PPP and Modem Client
Additional Settings
-
Connection Type
- Permanent
- On-demand (with timeout)
-
No Firewall
- Disables protection (not recommended for Internet use)
-
Route Type
- Default Gateway
- Specific Network
-
GPRS Support
- Higher speed and data-based billing [modem-g3 | Word]
SMS Configuration
Driver
SMS via GSM Modem
- No PPP connection required
- Requires SMS Transport enabled
Behavior
- Checks messages every 5 seconds
- Cannot process SMS during active PPP sessions
- Multiple modems:
- All receive
- Only second modem sends [modem-g3 | Word]
Multiple Interfaces
A G3 can support:
- Up to 2 modem connections
- Plus Ethernet
Total: 3 IP interfaces [modem-g3 | Word]
Interface Selection
Routing is based on:
- IP address
- Network mask
Example:
- Ethernet: 192.168.1.x → Ethernet
- Modem: specific IP → modem interface [modem-g3 | Word]
Default Route
| Interface | Method |
|---|---|
| Ethernet | Set Gateway ≠ 0.0.0.0 |
| Dial‑In | Remote Mask = 0.0.0.0 |
| Dial‑Out | Route Type = Default Gateway |
Only one interface can define default routing [modem-g3 | Word]
IP Routing
- Enables forwarding between interfaces
- Common use:
- Dial‑in → access Ethernet devices
Modem Status Monitoring
Function
GetInterfaceStatus(index)
Status Values
| Status | Meaning |
|---|---|
| CLOSED | Not initialized |
| INIT | Initializing modem |
| IDLE | No active connection |
| SMS | Processing SMS |
| CONNECTING | Establishing connection |
| CONNECTED | Link established |
| NEG LCP | Negotiating link protocol |
| AUTH | Authentication in progress |
| NEG IPCP | Negotiating network settings |
| UP | Active connection |
| HANGING UP | Disconnecting |
GSM Signal Strength
| Value | Signal |
|---|---|
| 0 | ≤ -113 dBm |
| 1 | -111 dBm |
| 2–30 | -109 to -52 dBm |
| 31 | ≥ -51 dBm |
| 99 | Unknown |
Approximate Signal Bars
| Range | Bars |
|---|---|
| ≤ -103 dBm | 1 |
| -101 to -95 dBm | 2 |
| -93 to -85 dBm | 3 |
| ≥ -83 dBm | 4 |
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