icalendar - In iCal format how would I specify a the contact person's phone number -

looking @ spec here: https://www.ietf.org/rfc/rfc2445.txt
have contact person event, have name, email , phone number.
see can add field:
organizer;cn=john smith:mailto:jsmith@host1.com
i'm not sure put phone number.

nb: i'm producer , primary consumer of feed, ideally others consume also. , using dday.ical generate feed.

suggested answer:
if don't mind if other consumers missing field... can use x-custom-field format?

edit:
i'm doing following, works me, i'm not sure other clients?
organizer;cn=john smith;tel=00000000000:mailto:john.smith@example.com

edit: in circumstances dday ical not formatting field correctly when though use same library encode , decode it. here's encoding method:

calevent.organizer = new organizer("mailto:"+detail.eventdetails.contactemail) {       commonname = detail.eventdetails.contactname,       parameters =       {           {"tel", detail.eventdetails.contactphone }       }                }; 

and outputs so: (missing spaces before :mailto...)

organizer;cn=neque porro quisquam est qui dolorem ips & quia dolo;tel=000 0  00 0000 or 000 000 0000 or 000 000 0000 :mailto:nequepo.porroqu@example.co  .nz 

there no standardized field this. in theory replace mailto: tel:, i'm not sure how clients respond.

p.s.: don't use rfc2445, use rfc5545, it's been out 6 years =). rule of thumb, obsoleted rfc have little "obsoleted by" note @ top of document.