Both PTFEs utilise the US Naval Observatory maintained co-ordinated Universal Time (UTC), obtained via the NAVSTAR Global Positioning System (GPS). In the temporary absence of GPS satellite received time, the Drumgrange PTFE will maintain precise time to an accuracy of:

• Caesium: less than 50µsec after 90 days without GPS
• Rubidium: less than 250µsec after 45 days without GPS