I need to know when a signal has zero frequency (0 Hz), but in pd vanilla an not extended version.
I know that this could be done by either [spigot~] or [<~] (/[>~]/ [=~]) objects, but none of them is part of pd-vanilla.
Is there a way to import them manually or can anyone think of a -very low cpu consuming- way to find out whether or not signal is 0 Hz ?

if by that you mean a 0 signal value you could use mod's relationals http://puredata.hurleur.com/sujet-9767-relationals, for spigot~ you can use *~
Things are more complicated if you want to tell if an external signal that you don't know anything about is at 0 hz.