Reading from the instruction booklet, it says - If the tamper rate is flashing at the rate of approximately 2 seconds on and 2 seconds off, your system may reguire servicing. (End of quote). Could be the backup battery needs replacing, which will be found on a sevice. It also says - If it's connected to a telephone line there may be a fault on the line. The tamper indicator will flash at the rate of half a second on and half a second off. Sorry I can't offer you any further help I'm waiting for an engineer to attend to my faulty system.
Charles
February 2007