electric window relays, 4 or 5 terminals?

[tvr keith]

Some while ago there was a thread on the Griff forum about fitting relays to speed up the windows. It was said that you need to use relays with 5 terminals and I don't understand why.
Surely a 4 terminal one will do connecting relevent terminals to;
earth
power
switch wiring
window motor
Anyone know why I would need the ones with 5 terminals?