US Patent 11268376 Downhole safety switch and communication protocol

A system includes a surface device, preferably positioned on a surface, a downhole device, and a wireline communications system. A downlink communication between the surface device and the downhole device occurs via Hopped Frequency Shift Keying (HFSK) voltage-modulated signals. An optional uplink communication between the downhole device and the surface device may occur via Frequency Shift Keying (FSK) current-modulated signals. The downhole device may comprise an addressable switch.