An OSC employs guards to protect the manufacturing shop where the magnetic radar-absorbing coating is manufactured. The Army uses this specific coating for a particular fleet of unmanned aerial vehicles (UAVs). The facility is under constant surveillance with the help of HD CCTVs. Within the OSC’s facilities is a Vector Network Analyzer (VNA) that measures the reflection and transmission properties of the coating over a range of frequencies. Guards protect the OSC’s anechoic chamber, and anyone entering must use an iris scanner and sign a physical form detailing their name and reason for being there. At the door is a huge sign reading “Authorized Personnel Only.” The OSC has implemented the following physical separation methods to secure its facilities, EXCEPT?