Witnesses at all hearings shall be examined orally under oath or affirmation, and a record of the proceeding shall be made and kept by the board. If any witness resides outside the State or through illness or other cause is unable to testify before the board or its member, agent or agency conducting the hearing or investigation, his or her testimony or deposition may be taken within or without this State, in such form as may be directed. All applications for taking such testimony or deposition must be made by motion.