Spektrum SPM1305 - Manual (Page 21)

21 SPEKTRUM TELEMETRY
Lap Trigger
The Lap Trigger is placed next to the track and projects an infrared
beam of light across the track that triggers the infrared sensor in the car
each time it passes. The receiver records each lap time and sends that
information to the handheld unit where it is displayed. Laps can then
be stored and recalled from the handheld unit plus the fastest lap is
displayed. A programmed delay of 2 seconds prevents double lap counts.
Installing the Lap Trigger Battery
Use 3/32" and 5/64" hex wrenches to unscrew the case
and install the 9-volt battery as shown. Reinstall the
case, being careful not to over-tighten the screws.
Note: A typical 9-volt battery will power the lap timer for 9
hours. For extended use, an optional AC/DC adapter is available.
Remove the 9-volt battery when operating the unit from AC power.
Mounting the Lap Trigger
The lap trigger should be mounted 8" to 36" above the racing
surface facing outward from the track. Facing the trigger outward
keeps the IR beam from crossing the track in more than one lane
preventing unwanted false triggering. Hook and loop strips make
mounting easy. Only one lap trigger is necessary at each track,
as a single infrared beam will trigger the lap timer in all cars.
Aim beam across lane to outside of track
Place sensor 8" to 36" above
racing surface