+ - Gossen Metrawatt Metrahit 1x/2x devices, driver gmc-mh-1x-2x-rs232:
+ Power on the device with the "DATA" button pressed. Additionally Metrahit
+ 2x devices must be configured for the respective interface type.
+ - Gossen Metrawatt Metrahit 2x devices, driver gmc-mh-2x-bd232:
+ The device must be configured for the respective interface type.
+ - Norma DM950: If the interface doesn't work (e.g. USB-RS232 converter), power
+ on the device with "FUNC" pressed (to power the interface from the DMM).