After White's 40-minute presentation at the FRR, Boris Nikitin gave a 10-minute summary of Group 4's activities. Although he did not dwell on them, this group also had conducted an important series of tests since the Mid-Term Review. First, they had to establish that the spacecraft-to-spacecraft radio and cable intercommunication systems would work without any interference from internal or external power sources. In addition, they had to verify the safety of the pyrotechnics used in the two spacecraft - for example, the explosive bolts reserved for emergency undocking. To prove that the radio waves from neither craft - especially from the powerful Apollo high gain antenna used to communicate with the ATS-6 satellite could detonate those pyrotechnic components, Working Group 4 had directed a series of radiofrequency radiation experiments. All of these tests had been favorably concluded. Just prior to the Flight Readiness Review, R. H. Dietz and his fifteen teammates had participated in the checkout of the American communication and ranging equipment that had been installed into the prime and backup Soyuz spacecraft and in electromagnetic compatibility tests of American equipment scheduled to be transferred into Soyuz during the mission.
Every spacecraft had its own electromagnetic environment created by the sum of all the electronic and electric components onboard. Just as an electric drill may affect television reception or as a citizen's band transmitter may affect FM radio reception, so too may the energy radiating from switches, fan motors, or power cables interfere with television cameras or communications gear. Electromagnetic compatibility (EMC) was not generally a problem when one party developed its own equipment for use in its own spacecraft. But the possibility of a problem with electromagnetic interference might arise when equipment from one electromagnetic environment was transferred to another. During January and February 1975, Soviet specialists had accompanied their counterparts to the Kennedy Space Center to check out their television camera inside the command and docking  modules for EMC. And during May, the Americans had taken their television camera, motion picture camera, headsets, microphones, and speaker boxes to Baykonur to determine if the electromagnetic environment of Soyuz interfered with their performance. The test team found that all the American equipment operated satisfactorily. Although the Soviet half of Group 4 had experienced some difficulty meeting project deadlines before the Mid-Term Review, those problems had been resolved. Nikitin could report at the ERR that all their joint work had been completed.25
Academician Petrov had a few questions for Nikitin. His main concern was radio receiver interference on the Soviets' 121.75-megahertz frequency. During Soyuz 16, the crew reported receiving broadcasts from commercial aviation sources transmitting on that frequency. Petrov had asked the Americans to help them get the international radio users to vacate that channel during the mission, but NASA had decided not to take such an action. So when Petrov asked Nikitin what plans had been made to deal with such interference if it developed during the flight, the Soviet chairman said that they would just try to identify the source and ask the transmittor to suspend broadcasts during the remainder of the mission. After some further discussion on this point, Walt Guy reported on Working Group 5.26
25. "Apollo Soyuz Test Project, Flight Readiness Review, May 1975," 25 May 1975, pp. WG-4-1 to WG-4-53; interview, Reinhold H. Dietz-Ezell, 6 June 1975; interview (via telephone), Dietz-Ezell, 24 Mar. 1976; and B. V. Nikitin and B. F. Ryadinski, "Apollon, ya - Soyuz! Kak slishite?" [Apollo, this is Soyuz! How do you read?], in Soyuz i Apollon, pp. 149-165.
Dietz-Ezell, 18 Feb. 1976; interview; Dietz-Ezell, 24 Mar. 1976; and
ASTP notebook, kept by Nicholson, for May-Nov. 1975.