In every case of adjudication (as defined in section 551 of title 5) which has been designated by the Commission for hearing, the person or persons conducting the hearing shall prepare and file an initial, tentative, or recommended decision, except where such person or persons become unavailable to the Commission or where the Commission finds upon the record that due and timely execution of its functions imperatively and unavoidably require that the record be certified to the Commission for initial or final decision.
In every case of adjudication (as defined in section 551 of title 5) which has been designated by the Commission for hearing, any party to the proceeding shall be permitted to file exceptions and memoranda in support thereof to the initial, tentative, or recommended decision, which shall be passed upon by the Commission or by the authority within the Commission, if any, to whom the function of passing upon the exceptions is delegated under section 155(d)(1)  of this title: Provided, however, That such authority shall not be the same authority which made the decision to which the exception is taken.
To the extent that the foregoing provisions of this section and section 155(d) 1 of this title are in conflict with the provisions of subchapter II of chapter 5, and chapter 7, of title 5, such provisions of this section and section 155(d) 1 of this title shall be held to supersede and modify the provisions of subchapter II of chapter 5, and chapter 7, of title 5.
For the purposes of this chapter the Commission shall have the power to require by subpena the attendance and testimony of witnesses and the production of all books, papers, schedules of charges, contracts, agreements, and documents relating to any matter under investigation. Witnesses summoned before the Commission shall be paid the same fees and mileage that are paid witnesses in the courts of the United States.
Such attendance of witnesses, and the production of such documentary evidence, may be required from any place in the United States, at any designated place of hearing. And in case of disobedience to a subpena the Commission, or any party to a proceeding before the Commission, may invoke the aid of any court of the United States in requiring the attendance and testimony of witnesses and the production of books, papers, and documents under the provisions of this section.
Any of the district courts of the United States within the jurisdiction of which such inquiry is carried on may, in case of contumacy or refusal to obey a subpena issued to any common carrier or licensee or other person, issue an order requiring such common carrier, licensee, or other person to appear before the Commission (and produce books and papers if so ordered) and give evidence touching the matter in question; and any failure to obey such order of the court may be punished by such court as a contempt thereof.
The testimony of any witness may be taken, at the instance of a party, in any proceeding or investigation pending before the Commission, by deposition, at any time after a cause or proceeding is at issue on petition and answer. The Commission may also order testimony to be taken by deposition in any proceeding or investigation pending before it, at any stage of such proceeding or investigation. Such depositions may be taken before any judge of any court of the United States, or any United States magistrate judge, or any clerk of a district court, or any chancellor, justice, or judge of a supreme or superior court, mayor, or chief magistrate of a city, judge of a county court, or court of common pleas of any of the United States, or any notary public, not being of counsel or attorney to either of the parties, nor interested in the event of the proceeding or investigation. Reasonable notice must first be given in writing by the party or his attorney proposing to take such deposition to the opposite party or his attorney of record, as either may be nearest, which notice shall state the name of the witness and the time and place of the taking of his deposition. Any person may be compelled to appear and depose, and to produce documentary evidence, in the same manner as witnesses may be compelled to appear and testify and produce documentary evidence before the Commission, as hereinbefore provided.
Every person deposing as herein provided shall be cautioned and sworn (or affirm, if he so request) to testify the whole truth, and shall be carefully examined. His testimony shall be reduced to writing by the magistrate taking the deposition, or under his direction, and shall, after it has been reduced to writing, be subscribed by the deponent.
If a witness whose testimony may be desired to be taken by deposition be in a foreign country, the deposition may be taken before an officer or person designated by the Commission, or agreed upon by the parties by stipulation in writing to be filed with the Commission. All depositions must be promptly filed with the Commission.
Witnesses whose depositions are taken as authorized in this chapter, and the magistrate or other officer taking the same, shall severally be entitled to the same fees as are paid for like services in the courts of the United States.
Any person who shall neglect or refuse to attend and testify, or to answer any lawful inquiry, or to produce books, papers, schedules of charges, contracts, agreements, and documents, if in his power to do so, in obedience to the subpena or lawful requirement of the Commission, shall be guilty of a misdemeanor and upon conviction thereof by a court of competent jurisdiction shall be punished by a fine of not less than $100 nor more than $5,000, or by imprisonment for not more than one year, or by both such fine and imprisonment.