If two or more radiographic tubes are controlled by one exposure switch, the tube or tubes which have been selected shall be clearly indicated prior to initiation of the exposure. This indication shall be both on the X-ray control panel and at or near the tube housing assembly which has been selected.
25 Pa. Code § 221.26
The provisions of this §221.26 issued under section 302 of the Radiation Protection Act (35 P. S. § 7110.302); and section 1920-A of The Administrative Code of 1929 (71 P. S. § 510-20).
This section cited in 25 Pa. Code § 221.35a (relating to fluoroscopic X-ray systems).