Optical transponder and receiver

Transciever is made up of two words from the old days of radio, Transmitter and Receiver. A transciever will receive signals and transmit signals or radio waves/light waves. A transponder only transmits a signal that may be timed, intermittent, or constant. The signal usually is just a tone, but may include voice.

A transponder would typically only automatically respond to a signal inquiring of it's presence or data. One possible example would be to identify a "friendly" entity in a combat scenario in order to avoid "friendly fire". A transponder is a transceiver but a transceiver is not necessarily a transponder.

One man's entropy is another man's not entropy...

I want my whole room to smell like the perfume in that little bottle, but entropy has trapped it on the liquid level and I can't smell it!!!

Oh, now the molecules are drifting into their proper places in the room so I can smell it! This surely is the order I want!

Life is anti-entropic. It moves energy from a lower to a higher state of organization, but not for long! Hence my tag line.

Yes, but then the only one that entropy makes any sense to are humans. Nature could give a rat's ass. To nature it's just another state, so big deal!