So that the controller can continue to do its work...

Classic remote data transmission from serial interfaces is on the way out due to the conversion of telephony (land lines and mobile communications) to package-oriented technology.

Modem connections via the analogue fixed network and "circuit switched data" in the G2 network are on their way to the technology museum. However, the challenge with controllers is that they use these technologies, have a long service life and changing a controller is frequently associated with high investments.

In the era of autonomously driving cars and fridges that order food, IP (internet protocol) is the measure of all things. A "call" from the land line to the serial interface of the controller is no longer possible, since the serial world cannot be addressed via IP.

Nothing can be changed in the controller and the remote data transfer software. Nevertheless, both should communicate encrypted via the Internet. For this, the outgoing data of the controller/remote data transmission software must be accepted as "modem" and translated to "IP". The incoming data then has to be translated back again from "IP" to "modem." The controller and remote data transmission software also have to believe that they are communicating with a modem. There are two solutions to achieve this.

The "silver" solution

This version requires a computer of the lift company with Internet access, the free software of the virtual computer ("base-Ser-IP"), the remote data transmission software of the manufacturer and an IP address accessible from the outside. The corresponding GSM module with matching interface and Internet-capable mobile communications card are needed on the controller.

Establishment of the connection is generally initiated by the controller. The "call" of the lift company in the lift is transformed by "base-Ser-IP" into an SMS, which triggers establishment of an encrypted connection of the controller to the IP address at the lift company. If the encrypted Internet connection has been established, the data are exchanged and appropriately transformed for both, controller and remote data transmission software.

The advantages:
• Independence through use of free mobile communications cards
• The controller remains

The disadvantages:
• Establishing the connection takes up to 30 seconds
• Costs for the SMS upon "call" by the lift company

The "golden" solution

The second solution consists of making the controller accessible via a mobile virtual private network (VPN). The controller is available via IP within this network. Internet communication can be established in this way. However, the initial investments for a mobile VPN for the lift builder are high, since it needs its own mobile VPN.

The service provider base engineering GmbH wants to offer its customers a more affordable solution. "Without having to going through the laborious and expensive process of installing a mobile VPN, the lift company can simply the use low cost roaming cards of base engineering GmbH for a lift emergency lift call combined with controller data transmission," explained the company. If these roaming cards are used, the base routing servers can be used free of charge. This provides the advantages of a mobile VPN without additional costs with a maximum reduction in work load for the lift company.

When using the base roaming cards, the remote data transmission software of the manufacturer connects with the base routing server via a VPN tunnel. The mobile communications card must be available via the base routing server under a fixed IP address. "base-Ser-IP" knows this IP address. When there is a "call", the connection to the controller occurs via the routing server in fractions of a second.

The advantages:
• Connection in seconds
• No costs through elimination of the SMS fees
• "base Ser IP" is part of the mobile VPN and as a result is no longer publicly available
• No high initial investment
• Easy to install

Conclusion

The connection of serial controllers via GMS to the Internet and as a result reading out is possible and does not have to be expensive. If the connection is initiated by SMS to the GSM module, you only need a data card. If you take the route via VPN, you need a provider with routing server.

Nadja Müller

base-engineering.com