Hi Drewbie, thanks for the idea, no I hadn't but I have now, unfortunately with no success. It may not be using the default user name/password so I am struggling. There is an SD card inside, for the firmware I believe, so I don't know if the password etc is in there or eeprom. I have ordered a Bus Blaster to try to get in through JTAG and have a look what's going on. I feel sure Symmetricom must have a back door user/password for when people mess up. There is, apparently also a "community" password to allow use of there GUI software which is downloaded from the 4370. Looking at the screenshots in the manual I think this may be "tsc" but I have to get that far first. Other than that the two units seem to be settling in, running them 24/7 for a week then check out the accurcy. After two days with 10 second sampling they are averaging within 1uHz of each other but I am not sure if the accuracy of a £100 FA2 frequency counter is to be trusted at that level. I am using one unit as the external reference and the other as the input, is this a valid test?