- USSR field switchboard housed in a wooden cabinet. PK-10
supported ten telephone lines - five with magneto signaling
and five more with phonetic signaling. Two similar PK-10
sets could be joined to provide for 20 subscriber lines. Our
sample was manufactured in 1945. The PK-10 field
switchboards have to be controlled by any UNA-FI telephone set
with phonetic and magneto signaling capabilities.