# RTK dial-in data link

Use a dial-in data link if you are obtaining RTK data by connecting to the modem at the base receiver using a phone number. RTK data is transferred using a cellular data call.

The modem you use for the connection determines how you will connect and configure your equipment.

Rover equipment setup considerations

At the rover, your controller and your receiver may each have an internal modem. You may also have another device that contains a modem, such as a mobile phone.

The modem you use at the rover for the data link depends on:

- which device contains the SIM card you want to use for the data.
- the method you want to use to connect the controller to the receiver.

The decisions you make determine how to connect your equipment and configure the Route through controller setting in the RTK survey style. The options are:

- When the SIM card is in the receiver, connect the controller to the receiver using Bluetooth or a serial cable and then set the Route through controller setting to No.
- When the SIM card is in the controller, connect the controller to the receiver using Bluetooth or a serial cable and then set the Route through controller setting to Yes.
- When the SIM card is in another device (for example, a mobile phone), connect the controller to the receiver using Bluetooth or a serial cable. Then do one of the following:
  - Connect the external modem to the controller and set the Route through controller setting to Yes.
  - Connect the external modem to the receiver and set the Route through controller setting to No.

- When using the modem in another device, you must use a serial cable to connect the receiver to the other device. Because most receivers have only one serial port, the connection from the receiver to the controller must be a Bluetooth connection. You cannot use Bluetooth to connect the receiver to the other device because the Trimble Access will not know the connection exists. If you are using a receiver with more than one serial port, such as the R8 receiver, the connection between the controller and the receiver can also be a serial cable.

- Modems used with Trimble Access must support Hayes compatible AT commands.

When using the modem inside another device, you can choose to route the incoming data through the controller.

- If you choose to route through the controller, the controller can use the Internet connection for other functions, including downloading projects and jobs or email during the RTK survey. You will need to connect the external modem to the controller.

- If you choose not to route through the controller, then the controller cannot use the Internet connection. Only the receiver will be able to use the Internet connection. You will need to connect the external modem to the receiver.

Base receiver equipment setup considerations

The modem at the base station must be able to accept dial-in data calls. Because the modem inside a Trimble controller cannot do this, you must use the modem inside the receiver. If you have another device that contains a modem, such as a cellular phone, you can use that instead of the modem in the receiver, as long as the receiver supports CTS (clear to send) flow control.

The modem you use at the base for the data link determines how to connect your equipment. The options are:

- When the SIM card is in the receiver, connect the controller to the receiver using Bluetooth or a serial cable.
- When the SIM card is in an external modem (for example, a mobile phone), the receiver must support CTS (clear to send) flow control. Connect the controller to the receiver using Bluetooth, or possibly a serial cable. Then connect the controller to the external modem using a serial cable.

- When using the modem in another device, you must use a serial cable to connect the receiver to the other device. Because most receivers have only one serial port, the connection from the receiver to the controller must be a Bluetooth connection. You cannot use Bluetooth to connect the receiver to the other device because the Trimble Access will not know the connection exists. If you are using a receiver with more than one serial port, such as the R8 receiver, the connection between the controller and the receiver can also be a serial cable.

- Modems used with Trimble Access must support Hayes compatible AT commands.

Software configuration

To configure a dial-in data link at the rover or the base, in Trimble Access:

1. Configure the RTK survey style for a dial-in data link and select the appropriate GNSS contact. See:

   - To configure a rover dial‑in data link
   - To configure a base dial‑in data link

2. Create a GNSS contact that specifies the contact information for the real-time correction source. See:

   - To create a GNSS contact for a rover dial‑in data link
   - To create a GNSS contact for a base dial‑in data link

To start the survey, see To start an RTK dial-in survey.