The modulator is good for both shortboard and longboard and C128. The second picture shows the longboard connection. For a longboard, GND must be connected to the motherboard and for the 12V VIC marking, the 2 contacts must be connected to each other. Needle and cable included. It gives a very clear picture. Tested

https://www.pcbway.com/project/shareproject/Commodore_64_and_128__C64___C128__RF_modulator_replacement.html