Interoperability is enabled between participants in a network by determining values associated with a value metric defined for at least a portion of the network. The first beam intersects a thin metal film and engenders a first surface plasmon wave thereon. The monitoring unit is mounted on the vehicle to monitor a signal indicative of the air pressure detected by the sensor unit so as to watch a decrease in the air pressure. Furthermore, the above ground invention can be mounted on a side of a fence. When the primary resonator is closed by the optical switch, and pulses are not being amplified, CW radiation is generated in the secondary resonator and prevents the gain-medium from being saturated.