1558A APS
3-8
Operation
Pwr A Terminals (-DC, RTN): These two terminals are
used to connect an external -20 to -56 VDC power source to
the 1558A. The positive side of the external power source
should be connected to RTN and the negative side to -DC.
Pwr B Terminals (-DC, RTN): These two terminals are
used to connect a redundant (second) external -20 to -56
VDC power source to the 1558A. The positive side of the
external power source should be connected to RTN and the
negative side to -DC.
Alarm Terminals (Com, NO, NC): These three terminals
are used to connect the APS unit alarm relay contacts to
external alarm alert equipment. The APS unit alarm relay
contacts can be wired as Normally Open or Normally
Closed. The contacts are rated at 2 amps @ 30 VDC. When
the APS is powered, the alarm relay is in the operated state
and the NO (normally open) contacts are open and the NC
(normally closed) contacts are closed.
3.5
Option Switch Functions
The 1558A rear panel has four 8-position DIP switches for
configuration purposes. Refer to
Section 2.5.1 on page 2-3
and the 1558A Configuration Guide at the end of this man-
ual
for instructions on setting switches. The following para-
graphs explain the operational functions of these switches.
Switch S1
Block/Pass FDL: The 1558A can be configured to either
block or pass the 4 kb ESF facilities data link (FDL) from
the NET A/B path to the DTE port and from the DTE port to
the NET A/B ports.
Regenerate/Pass CRC: The 1558A can be configured to
either regenerate or pass CRC from the network to the DTE
port and from the DTE port to the network.
Master/Slave: The 1558A can be configured as either a
master or slave unit. The key difference between a master
and slave 1558A unit is that a master 1558A unit can access
and control a remote slave 1558A but a slave unit cannot
access and control a master.unit.
ARM ROM /RAM: The 1558A can be configured to boot
the alarm thresholds from either the ROM or from the unit’s
RAM. The ROM defaults are ES = 20, CSES = 2, LOS =
Yes, LOF = Yes, and Line Availability Timer = 60.
Boot Modes: The 1558A unit configuration can be set at
power up by the parameters stored in the ROM, RAM,
option switches, or from the optional 1559 site manager.
Switch S2
Framing Errors: The 1558A can be optioned to alarm
based upon receipt of 32 or more consecutive framing
errors. This parameter can also be disabled.
Loss of Signal: The 1558A can be configured to alarm
based upon loss of signal for > 175 bit intervals. The param-
eter can also be disabled.
AMI/B8ZS: The 1558A can be configured for either AMI
line coding or B8ZS line coding.
CSU Mode: The 1558A can be configured to ignore CSU
loop and performance commands (disable) or to respond to
CSU loop and performance commands (enable).
Path Revert: The 1558A can be configured to revert back
to Path A after a failure (enable) or to remain on Path B
(disable). Revert should be enabled if the user has a prefer-
ence for the Path A loop facilities.
DTE Framing: The 1558A DTE port can be configured to
operate in the D4 framing mode or in the ESF framing
mode. Note that the NET A and B paths are always operated
in the ESF mode.
Switch S3
If multiple 1558A units are co-located at a site and if the site
is being managed by a 1559 APS site manager, this eight
position DIP switch is used to configure a unique address
for each of the 1558A units being managed by the 1559.
Typically, there will not be a 1559 located with the 1558A
and the factory default address (Address 1/2) can be used
(all switches in the OFF position). If multiple units are
located with a 1559, simply set each unit to a unique address
using Switch S3 (see the Installation chapter for instructions
on setting addresses).
Switch S4
Option Switch S4 is used to configure the LBO value for the
NET A and NET B ports and the DSX level for the DTE
port The NET A and NET B LBO value that can be set are
0, 7.5, 15.0, and 22.5 db. The DTE DSX values can be set
for 133 feet, 266 feet, 399 feet, 533 feet, and 655 feet.
The next section discusses the general operation and use of
the LAPS (Local Access Protection Switch) software.
