the use of 'l' in l'on peut vous joindre

In 4.3 Booking a table, what does the 'l' refer to in the phrase ' ou l'on peut vous joindre '

The 'l' refers to the telephone number, which is implied by the "on" in the English translation, ie: "Avez-vous un numéro de téléphone où l'on peut vous joindre" (où=where) Do you have a telephone number (where) we can contact you on (the telephone number)?

Many thanks- very helpful and clear response

Thanks also for the response, but I find I am still looking for some clarification. In effect , you are saying the où l' is an abbreviation of où le, le referring to le telephone, and roughly equivalent to "on (the) which", which in turn implies the "on" has more to do with the où, and "the which" is the definite article, le. What's needed is to show some other examples of usage, preferably using a different verb, and preferably where the definite article is not abbreviated, so that its gender reference is unambiguous. Do any such examples come to mind? For example, could/should I say Est-ce qu'il y une adresse où la je peux l'envoyer?, for Is there an address where I can send it? (for some masculine "it")

Bonjour à tous! Let me clear this up for you. "Avez-vous un numéro de téléphone où l'on peut vous joindre" The l' in this sentence has no meaning. In the French language there is a big emphasis put on the sound and flow of the language. The l' serves to make the sentence flow better because without it, a vowel followed by another vowel in French sounds very cumbersome. This catches many people out, especially because object pronouns are hard enough in French without chucking another one in there that doesn't even mean anything. I hope this has cleared things up! Continuez comme ça! Keep up the good work! - Marie-Claire