An actuator assembly may comprise a housing, a shaft, a shape memory alloy torque tube, and first and second unidirectional bearings. The reference pulse has a higher probability of containing more than one photon than the signal pulse. The metal plate is fixed to the top of the stationary rod and clamped between the front casing and the rear casing, and the stationary rod is fixed to the rear casing and extends downward out of the rear casing. The first message is for a second end point that communicates using a second protocol, such as SIP.