When the power is re-connected to a tachograph head there is a power surge indicated by a straight line deflection from the base line straight to the top of the tachograph chart

    Indicated here  A

This may occur where the fuse has been removed, which would show that the vehicle had been stationary when in fact it had been moving

    Indicated here B

To reconnect the fuse the head may well be opened, so that the fuse can be re-inserted.  When the head is opened there will be small ticks on the traces, where the styli disengaged from the chart.

    Indicated here  C

If there is a power reconnection, which is preceded by a stationary period and there are small ticks on the chart at the same place consider, that the power supply may have been tampered with i.e., fuse removed or isolation switch.

There are of course legitimate reasons for this type of trace to occur. i.e. where the battery is disconnected for repairs, or there has been a jump-start, but always be wary.

 This type of occurrence will be indicated on the analysis as a K fault