2.12.3
Locks and Key-Lock-Operated Switches
**************************************************************************
NOTE: Either round key or conventional key type
locks as defined in this specification are
acceptable. Selection should be based on hardware
availability at the time of design and the
requirement for matching locks currently in use at
the site. If the locks do not have to be matched to
locks in use at the site, and the designer has no
preference as to lock type, all brackets may be
removed.
**************************************************************************
2.12.3.1
Locks
Locks required to be installed on system enclosures for maintenance
purposes shall be UL listed, [round key type, with three dual, one
mushroom, and three plain pin tumblers] [or] [conventional key type lock
having a combination of five cylinder pin and five-point three position
side bar]. Keys shall be stamped U.S. GOVT. DO NOT DUP. The locks shall be
so arranged that the key can only be withdrawn when in the locked position.
All maintenance locks shall be keyed alike and only two keys shall be
furnished for all of these locks.
2.12.3.2
Key-Lock-Operated Switches
Key-lock-operated switches required to be installed on system components
shall be UL listed, [with three dual, one mushroom, and three plain pin
tumblers,] [or] [conventional key type lock having a combination of five
cylinder pin and five-point three position side bar]. Keys shall be
stamped U.S. GOVT. DO NOT DUP. Key-lock-operated switches shall be two
position, with the key removable in either position. All key-lock-operated
switches shall be keyed differently and only two keys shall be furnished
for each key-lock-operated switch.
2.13
SYSTEM REQUIREMENTS
2.13.1
Signal Transmission Format Code
**************************************************************************
NOTE: Different FO systems may use different
modulation methods and codes. For example, the
digital signal may turn the light source on or off,
it may use frequency shift keying, or it may cause
the intensity to shift between two preset levels.
Likewise, the code can be the simple NRZ (non-return
to zero), or it can be the more complex and
efficient RZ (return to zero) code, such as the
Manchester code. The modulation method can be
important to bandwidth limited systems since some
methods required twice the bandwidth of other
methods for transmitting the same data.
**************************************************************************
FO equipment shall use the same transmission code format from the beginning
of a circuit to the end of that circuit. Different transmission code
formats may be used for different circuits as required to interconnect
supported equipment.
SECTION 16768A
Page 23
Previous Page
