A virtual wire connects two ends of a controlled system using a radio frequency (RF) medium. The transmitting-end is hard-wired to the physical source control(s), e.g., foot pedal. The receiving-end is hard-wired to the device(s) being controlled, e.g. electro-surgical generator.
On activation of the source controls, the transmitter sends a continuous stream of data packets to the receiver. Each data packet indicates the current state of the source controls. The receiver actuates the associated device(s) as directed by control information in the data packets. If the stream of data packets ceases, for any reason, then the receiver must turn off all devices being controlled, i.e., enter a fail-safe state.
The key element of the virtual wire paradigm is to provides a fail-safe mechanism based on a loss-of-signal (LOS) condition. LOS at the receiver-end is defined as the absence of the transmitters continuous data packet stream. If the receiver detects a LOS, it enters a fail-safe state, that typically results in deactivation of all devices being controlled.
A virtual-wired system is analogous to a hard-wired system, in that a switched electrical current flow gates the activation of a device; if the electric current flow ceases, for any reason, then the controlled device deactivates.