Additional Components - Nortel DMS-100 Series Maintenance Manual

Protection switches are initiated automatically by the RCS or SMS,
manually by operating company personnel using the CARRIER level
protection switch (PROTSW) command, or during execution of the far end
loop test (FELP) command. The FELP command enables a continuous loop
back on all 24 DS-1 channels of a specified link.
When a protection switch occurs, calls in the talking state are maintained.
For plain ordinary telephone service (POTS) and coin lines, calls in the
ringing state are also maintained. The protection line carries voice and
signaling information, and if the A-link (or C-link in Mode II) is protection
switched, system control information as well.
Protection link configuration

Additional components

Not applicable.
Network
RCS
DS-1 primary links
DS-1 protection links
DMS-100 Family SMS Maintenance Manual XPM10 and up
SMS
RCS RCS
SMS hardware 2-7
Unprotected
module