Medical support arm device and medical system

A medical support arm device comprising:

• a brake provided in at least one joint of a plurality of joints that define a deployment configuration of a multi joint arm, and configured to release a rotation shaft of the at least one joint when electricity is supplied to the multi joint arm and lock the rotation shaft when electricity is not supplied to the multi joint arm, wherein
• when electricity is not supplied to the multi joint arm, the brake is configured to exert a brake force that supports a weight of the multi-joint arm to maintain the deployment configuration of the multi-joint arm, but also permits rotation of the rotation shaft by an external manually applied force equal to or larger than a predetermined value,
• the medical support arm device is an observation device that includes imaging circuitry;
• and
• power supply control circuitry configured to control a driving of an electric power supply to the multi joint arm and the imaging circuitry, the power supply control circuitry is configured to remove a supply of electricity from the electric power supply to the multi-joint arm, and preferentially supply electric power to the imaging circuitry, when an interruption of electrical power is experienced.