[jQuery] [validate] Make at least one input field required

[jQuery] [validate] Make at least one input field required


html looks like:
<input type="text" id="email" name="email">
<input type="text" id="tel" name="tel">
<input type="text" id="gsm" name="gsm">
i want people to fill in at least one of these fields
how can this be done using the jquery (validation plugin)?