It automatically detects and reads from devices following the HID USB protocol. For this type of detector, a comparator detects each time an ac pulse changes polarity. The camera automatically records whenever it detects movement in view. The operating system detects the presence of an SSD and optimizes operation accordingly. The radio receiver connected to the receiving antenna detects this oscillating current and amplifies it. Second, it detects cable length and adjusts the power used for transmission accordingly. It vibrates when it detects concealment and lies. Screening consists of a blood test that detects anti-hepatitis C virus antibody. However, K9 detects the android Romana and eliminates it. A type of polymerase chain reaction that detects the virus's RNA is more accurate. Nuclear magnetic resonance detects atoms with different gyromagnetic ratios. Using a cryptographic hash and a chain of trust detects malicious changes to the file. Such a system detects and shoots down incoming projectiles before they reach the vehicle. The victim detects little abnormal sensation as the oxygen level falls. The semicircular canal system detects rotational movements.