US Patent 8251994 Vessel sealer and divider with blade deployment alarm

An electrosurgical forceps includes a selectively advanceable knife and a knife deployment alarm configured to emit a signal under predetermined conditions. An alarm is configured to emit a signal when the cutting blade moves relative to the blade channel. A series of resistances are arranged so that a shorting of each resistor is indicative of a predetermined operating condition triggering the alarm to emit a signal. Pressure sensors, optical measurement devices, and electrical contacts are envisioned for determining blade or trigger actuation or translation.