The popular SP15C (SSD in-car chip) changes wires to become compatible with the plug-and-play Slot.it and Policar new connector system. Check it out in the new manual:

http://slot.it/wp.../uploads/2021/01/28-SP15Manual.en.pdf

This unit will adapt any Slot.it car for operation on a Scalextric Digital system. Soldering required for installation. This chip is designed to handle more amperage than Scalextric's own digital chip, which allows you to run somewhat more powerful motors and/or stronger magnets on your cars without blowing the chip.

External infrared LED on wires may be used (available separately).