Practice Section 810258X
8Rev C 2/5/97
Alarm Cutoff, System Ground, and Test Connections
3.18 Alarm cutoff, system ground, and test connections are made to connector P4, a three-pin
wire-wrapping terminal, as described below.
• Grounding the ACO (alarm cutoff) pin turns off external alarm indicators (typically, these
are external audible alarms). The ACO pin is normally connected to ground via a push-
button (or other switch) that allows for manual activation of the ACO function.
•TheTST (test) pin is connected to the GND (system ground) pin to perform a flash down-
load of system software when doing a firmware upgrade. Please refer to the Tellabs
2500-Series Universal Firmware Download Program (UFDP)
manual (practice section
812500UFDP) for instructions on performing such a firmware upgrade.
Option Switch Overview
3.19 The dual in-line packaged (DIP) switches (S1 through S4) enable the user to:
• determine how the assembly’s backplane bus and Control Port are partitioned (S2).
• when multiple assemblies are deployed on a daisy chain, set a unique shelf address
(position on the chain) for each mounting assembly (S4).
• identify the mounting assembly as the last (or only) assembly on a daisy chain (S1 and
S3).
Instructions for setting these switches are provided below.
Switch Settings and Cable Connections for Assembly Partitioning
SPLIT SHELF Option Switch Settings
3.20 The SPLIT SHELF switch (S2) allows partitioning of the 258X assembly’s backplane bus,
which normally addresses all 16 echo cancellers in the shelf, into 2 groups of 8 cancellers
each. With the assembly configured for one 16-canceller group, a single Control Port is
established. With the assembly partitioned into two 8-canceller groups, two separate Control
Ports are established, with Control Port #1 addressing cancellers 1 through 8 and Control
Port #2 addressing cancellers 9 through 16. Details on these arrangements follow.
3.21 With S2 in the OFF (down) position, a single Control Port addresses all 16 echo cancellers in
the assembly. Up to eight 258X assemblies optioned in this manner can be daisy-chained to
DTE via their Control Ports, in which case up to 128 echo cancellers are addressed via a sin-
gle Control Port (see note below). Refer to paragraph 3.17 above for baud-rate option selec-
tions and to Table 3-1 below for a switch setting summary. Information on making Control-
Port daisy-chain connections appears later in this section.
Note: Although up to 8 assemblies (128 echo cancellers) can be daisy-chained via
the Control Port, Tellabs recommends that users minimize the chaining
together of Control Ports for the following reasons:
1. If the baud rate is not at maximum or if simultaneous status changes
occur on many channels on the link, the cumulative echo canceller
response time (for status changes) can increase drastically. This either
slows traffic down on the switch or slows the activation of echo cancella-
tion at the beginning of the call.
2. If the Control Port fails, communication is lost to
ALL
channels.
3.22 With S2 in the ON (up) position, two separate Control Ports that address eight cancellers
each are established for the mounting assembly. Some customers use this capability to
ensure that the individual channel-control activity is not blocked or disrupted in any manner
under high-traffic conditions on the bus. Refer to paragraph 3.17 above for baud-rate option
selections and to Table 3-1 below for a switch setting summary. Please be aware that Con-
trol-Port daisy-chaining of 258X assemblies optioned for two Control Ports is not possible.
