Wearable electronic devices, for example wearable camera systems, and methods for attaching electronic devices such as camera systems to eyewear or other wearable articles are described. The shut-off element has a longitudinal axis of symmetry and is designed to deform symmetrically. If a number of security tokens granting rights to use the common test feature are available, the program code enables the common test feature on user-selected ones of the hardware components that provide the common test feature, as permitted by the number of security tokens. Once the data packets are transmitted or received, the Ethernet controller may be configured to operate in an idle power state to reduce energy consumption. The instrument has a second set of connections by which the second tissue treatment electrode can be placed in circuit with the third electrode such that, in use, a current path is established therebetween.