The Curtis Protocol, an aircraft control interface, is provided. An elongate slot is formed in base member and the slot communicates with an elongate recess. The insects may be either male or female and may include mosquitoes. The film structure includes therein a semiconductor element such as a thin film transistor, a MOSFET, a bipolar transistor, a solar battery, etc. At least one removeable spacer is positionable between the idler support block and the frame to adjust relative positions thereof. A locking device is provided in the coupling arrangement and comprises a locking member arranged to be brought into contact with the plunger when this is in its outer position and to prevent the plunger being displaced from this position.