how to switch light on/off in a slotcar?

Hi,

I have an analog slotcar track and I want to switch the lights of the car(s) on/off, even when the cars stand still.

it can be done using Permaloog (permanent power AC and analog driving DC)
(sorry, this is a dutch site ,but the images speak for themselfs.)
(sorry, this is my first post ( can't use an external link ))

Permaloog uses a 20Khz AC signal ( blocksignal between +12 volt and -12 volt).

I want to mix this signal to the power of a analog slotcar track ( 4 lanes ) and switch this 20 Khz signal on and off ( bij hand or bij microcontroller).

Has anyone an idea how to do that?

thanks,

slotcar330p4