The OTT ecoLog 800 includes a GSM modem with SMA antenna connector that is used for remote data transfer and remote parameterizing through the GSM cellu- lar network (GSM = Global System for Mobile communications). The remote data transfer can be optionally carried out by SMS text messages or using the packet oriented mobile radio transmission service GPRS (General Packet Radio Service).If necessary – e.g. when the signal strength of the cellular network is low at the installation site – the factory installed radio antenna may be replaced by an exter- nal one.