The importance of hardening the SAFEGUARD System to EMP was established in the turbulent arguments of complexity and potential vulnerability of any ABM system during the deployment debates of the late 1960s. During the course of the considerable effort to achieve the operational Grand Forks Tactical Site, a unique problem was posed by the over 40 miles of buried conduits which formed part of the shielding for the control and power cables connected to each missile cell. Since these conduits were buried less than a skin depth deep, they constituted major receiving antennas for EMP and lightning. It was recognized that a nondestructive test technique was needed that would permit verification of the shielding provided by the conduits, initially to verify adequacy of construction, and periodically through the system life to insure that rust, freezing, or ground movement had not degraded the conduit system in such a way as to compromise the protection afforded by it. The Harry Diamond Laboratories was tasked by SAFEGUARD Systems Command to develop such a technique. A dual-loop version of Pulsed Loop Antenna Conduit Electromagnetic Radiator (PLACER) was used during the preliminary experiments to excite a buried conduit. The loops were driven in parallel by discharging a storage capacitor across a spark gap in series with each loop terminated in 40 ohms. Thus PLACER was simply a pulse-driven series LRC circuit.