The list of currently available media for providing such a ring cavity 202 include electrical cable, coaxial cable, {TAIL ~ reverberation lines}, delay lines, fiber optical cable and {HEAD ~ microwave cavities} 
The list of currently available media for providing such a ring cavity 202 include electrical cable , coaxial cable , { TAIL ~ reverberation lines } , delay lines , fiber optical cable and { HEAD ~ microwave cavities }
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD