(a) When, how, and by whom taken. For good cause shown, the testimony of any witness may be taken by deposition in any proceeding, when a complaint has been filed, whether at issue or not. Depositions may be taken orally or upon written interrogatories before any person designated by the hearing examiner and having power to administer oaths.

(b) Application. Any party desiring to take the deposition of a witness shall make application in writing to the hearing examiner, setting forth the reasons why such deposition should be taken; the time when, the place where, and the name and post office address of the person before whom the deposition is to be taken; the name and address of each witness; and the subject matter concerning which each witness is expected to testify.

(c) Notice. Such notice as the hearing examiner shall order shall be given for the taking of a deposition, but this shall not be less than 5 days' written notice when the deposition is to be taken within the United States and not less than 15 days' written notice when the deposition is to be taken elsewhere.

(d) Taking and receiving in evidence. Each witness testifying upon deposition shall be sworn, and the adverse party shall have the right to cross-examine. The questions propounded and the answers thereto, together with all objections made, shall be reduced to writing, read to the witness, subscribed by him, and certified by the officer. Thereafter, the officer shall seal the deposition, with two copies thereof, in an envelope and mail the same by registered mail to the hearing examiner. Subject to such objections to the questions and answers as were noted at the time of taking the deposition and would be valid were the witness personally present and testifying, such deposition may be read and offered in evidence by the party taking it as against any party who was present or represented at the taking of the deposition or who had due notice thereof. No part of a deposition shall be admitted in evidence unless there is a showing that the reasons for the taking of the deposition in the first instance exist at the time of hearing.