SIM Card Settings
The APN and general SIM card settings for RLTK421 can be configured in this section. To access the settings menu:
- Network
- SIM Card
follow these menus.
APN Settings
From the section in the Config part, WAN_4G Settings should be selected. After entering the settings, click the Save & Apply button to save the settings.

| Parameter | Description | Default |
|---|---|---|
| APN | Please set the correct APN address provided by the operator. | Autocheck |
| Username | APN username. | None |
| Password | APN password. | None |
| Auth Method | APN authentication type: None / PAP / CHAP. | None |
| Network Type | Specifies the type of network to be used: AUTO / 2G / 3G / 4G. | AUTO |
| Priority of Network Search | Allows you to set the network search priority: AUTO / 2G / 3G / 4G. | AUTO |
| PIN Enable | Enables the SIM card's PIN code. | Disable |
| EHRPD Enable | Enables or disables the EHRPD feature when using a 3.5G network. | Disable |
| LTE BANDLOCK | Specifies the LTE band mode: LTE FULL-BAND or LTE-TDD. | LTE FULL-BAND |
Ping Detection Settings
From the section in the Config part, Ping Detection Settings should be selected. After entering the settings, click the Save & Apply button to save the settings.
Ping detection is used to check the network status of the device and is disabled by default. After enabling this function, the device will attempt to ping the specified address and will retry after reaching the number of consecutive failures. It is recommended to enable this setting to avoid being dropped from the network by the base station when no data is sent for a long time.

| Parameter | Description | Default |
|---|---|---|
| Enable | Enables or disables the ping monitoring feature. | Enabled |
| Interval | The time interval for sending pings (5–86400 seconds). | 10 |
| Primary Server | The primary address to ping (IP or domain name). | 114.114.114.114 |
| Secondary Server | The secondary address to ping (IP or domain name). | 8.8.8.8 |
| Max Ping Tries | Retry when the number of consecutive failed ping attempts reaches this value (a value between 1–100 can be entered). | 4 |
Mobile Information
From the section in the Config part, Mobile Information should be selected. Users can check the detailed configuration information of their SIM card.

- The unit of signal strength is dBm and ASU. dBm=-113+2*ASU is calculated.
- RLTK421 supports displaying signal strength via ASU. ASU values range from 1 to 31, and the higher the value, the better the signal strength.
- Generally, if dBm ≥ -90 dBm, ASU ≥ 12, the signal is normal.