This is the Robitronic Lap Counter System with Three Transponders.

FEATURES: Robitronic's Lap Counter is a fully operational lap counting
system for all RC-Models of all size. The transponders are
extremely small and can be mounted without a problem in
mini RC cars.
_ Each tiny and featherweight transponder is encoded with a worldwide
unique number. By crossing the start/finish line the emitted
signal will be recognized and processed by the receiver module
to the lap counting bridge.
The system is capable of processing many transponders simultanously
and independent from the number of receiver modules installed. The
number of receiving modules required just depends on the track
width under the counter bridge.
For indoor and outdoor tracks
Works with unlimited number of cars running at the same time
Small, lightweight transponder
Professional software for all Windows Systems
INCLUDES: 3 Personal transponders (RS163)
4 Receiver modules for tracks with 4.9' (1.5mm) width (RS164)
PC-interface with data cable (RS165)
RCM-Beginners-Software with traning program

REQUIRES: A PC with Windows operating system
A lap counting bridge must be constructed over a section of the
track.

SPECS: Transponder Length: 7/16" (12mm)
Transponder Width: 5/8" (16mm)
Transponder Height: 5/16" (7mm)
Transponder Weight: .10oz (3g)

COMMENTS: For separate or replacement parts order:
Personal transponder - RBOM1630
Receiver module - RBOM1640
Interface module - RBOM1650