Not sure how 'common' this is, but during phone calls I will often agree to call somebody with the sole intention of letting the phone ring so that the other party knows that whatever event we agreed on has occurred. The most common example would be to let them know I have arrived at their place and am expecting them to come out whilst I wait in the car for example.
In Slovak and other Slavic languages there is a specific verb for this ("prezvonit",
to ring), yet in English I always end up with awkward constructions explaining explicitly that they shouldn't pick up.
Is there any informal way of communicating this easily in English or am I the only one cheap enough to try and save myself a couple of cents and has no such word developed in the English language?