Example 1. Reading of an electric meter via GSM and GPRS


Details of the example scenario:

  • The readings of an electric meter are to be taken every 10 minutes. Due to this being so frequent, the meter will be accessed via GPRS instead of by GSM calls in order to reduce costs.
  • The energy provider (Endesa, Iberdrola, etc.) will make a conventional GSM call to carry out a meter reading once a day.
  • The GSM call must take priority. When the modem receives a call from the energy provider, it must “freeze” GPRS communications to give way to the readings carried out by the provider. Once the GSM call is terminated, GPRS connections must be reestablished.

Proposed solution using MTX-65i and MTX-Tunnel.


  1. Readings of the electric meter are continuously carried out via GPRS and in real time from the office.
  2. When the electricity provider (Endesa, Iberdrola, etc.) makes the daily GSM call to the modem to read the meter, GPRS communications are frozen to give way to the call from the provider which takes priority.
  3. Once the GSM call is terminated, real time GPRS communications are established.


Configuration files for the MTX-Tunnel for the proposed solution:

This configuration is what must be inputted in the configuration file of the modem to be able to carry out the implementation described in the scenario.


 COMM_baudrate: 9600 Speed of the serial communication port with the PLC
 COMM_bitsperchar: 8 Number of data bits
 COMM_autorts: off No flow control
 COMM_autocts: off No flow control
 COMM_stopbits: 1 Configure 1 stop bit
 COMM_parity: none No parity bit
 GPRS_apn: movistar.es APN GPRS provided by the GSM operator
 GPRS_login: MOVISTAR Login GPRS provided by the GSM operator
 GPRS_password: MOVISTAR GPRS password provided by the GSM operator
 GPRS_timeout: 0 The modem will be permanently connected
MTX_mode: server GPRS connection in server mode
 MTX_model: MTX65i Modem model
 MTX_ping: 35 Ping frequency to supervise the connection
 MTX_pingIP: IP (for example) of Google so the Ping can be carried out
 MTX_radioBand: europe GSM band in Europe
 MTX_rssiLevel: 10 Red LED shown when network coverage is poor
TCP_port:20010  TCP port to establish the serial GPRS Gateway
 Firewall_enabled: off Firewall deactivated
CSD_enabled: on Allows GSM calls to be received from the energy provider (Endesa, Iberdrola, etc.)