[fa.telecom] What does "metallic" mean?

vail@LOCUS.UCLA.EDU ("Theodore N. Vail") (09/16/85)

Section 68.302 (d), of the FCC rules and regulations concerning
connection of terminal equipment to the telephone network an,d entitled
"Metallic voltage surge" requires that the equipment be subject to
"Two 800-volt peak surges of a metallic voltage (one of each polarity)
having a 10 microsecond rise time to crest and a 560-microsecond minimum
decay time to half crest applied between (1) tip and ring of a two wire
connection ..."

Other sections of these FCC rules refer to "voice band metallic signal
power" and "metallic surges".


Does anyone know what "metallic" means in this context?

ted