.841.
, , , , .. .
, (, ) , .
, , /, .
, /, .
, (, ) .
, .
(span) - / .
(APS) - , NMS () , NMS, .
, , .
, ( ).
(protection channel) , . .. ( () APS).
(SP) , , , () , , .
MS SPRinq - .
( NUC) - MS SPRing, APS ( ). : - .
(NUT) - , ( MS SPRing), APS.
(RS) - - , -, , ( ) , ( ) (. . G.707).
(SS) - - APS 1:1, 4- , . SS , ( RS).
(squelching) - AU-AIS .