Method for assembling a hair cutting appliance

A method for assembling a power transform module for use with a hair cutting appliance, the hair cutting appliance comprising a body having a consumer actuated power switch, a power source in electrical communication with the power switch, a drive system positioned within the body in selective electrical communication with the power source, at least one cutting unit coupled to the drive system and comprising an external cutting member, a control circuit positioned within the body, a switching element in electrical communication with the control circuit, the switching element switchable by the control circuit between a conducting state to electrically connect the drive system and the power source and a non-conducting state to electrically isolate the drive system from the power source, the method for assembling the power transform module comprising:

• providing at least one optical sensor within a housing;
• providing at least one optical source within the housing;
• wherein the housing of the power transform module is configured to be mounted to the body such that upon mounting the power transform module to the body;
• the at least one optical sensor and the at least one optical source are in communication with the power source;
• the at least one optical sensor is in electrical communication with the control circuit;
• the at least one optical source is configured to project an optical signal at an area in front of the external cutting member;
• the at least one optical sensor is configured to sense a pre-defined skin-hair edge in the area in front of the external cutting member;
• and wherein the switching element is configured to be switched by the control circuit to the non-conducting state when a first sensed condition of the at least one optical sensor exceeds a first-preprogrammed threshold stored by the control circuit.