The ability to use a phone to access a meeting is useful for individuals who are on the road or otherwise cannot attend a meeting using a mobile device or PC. With Skype for Business PSTN Conferencing, users in your organization can host or create meetings that contain dial-in phone numbers. Callers can then use those phone numbers to call into a meeting using their phone. You only need to set up dial-in conferencing for users who plan to schedule or lead meetings. Unless the organizer has locked the meeting, anyone who has the dial-in number and conference ID can join the meeting.