Ebstarit,try these:
1, Turn off the TVM50.
2, Set the mode switch at the side to 5 (switch 1 and 3 to ON)
3, Turn on the TVM50
4, Confirm that the Run Indicator blinks 5 times.This may take a few minutes. The Alarm Indicator and Run Indicator will first blink
intermittently before the Run Indicator blinks 5 times.
5, Turn off the TVM50
6, Set the mode switch back to 0
7, Turn on TVM50 again