Pub. 42004-735L2D
M
ODEL
LE300
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ERIES
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ALL
-M
OUNT
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AGE
/P
ARTY
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XTENDERS
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p:\standard ioms - current release\42004 instr. manuals\42004-735l2d.doc
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Echo Cancellation
Line echo (also known as electric or hybrid echo) is created by the electrical circuitry connected to a two-
wire (full duplex) audio system. Echo is inherent in all full-duplex audio systems and is affected by the
audio line length and line impedance mismatches. The presence of audible echoes results in undesirable
audio quality. This kind of quality degradation is inherent in network equipment and end-user phone
devices.
To minimize echo, the Model LE300 performs an echo cancellation sequence on party lines 1 through 5.
The echo cancellation process takes approximately 15 seconds and is performed automatically one minute
after power is applied to the LE300. This delay allows all power levels to stabilize prior to performing
echo cancellation.
N
OTE
:
Signal impulses are transmitted onto the party lines during the echo cancellation process. Handset
stations that are in use on a party line will hear the signals in the handset receiver. For troubleshooting
purposes, the one-minute delay may be disabled by closing DIP switch SW6 position 1. Refer to Figure 7
for the location of SW6 on the Main PCBA and the table below for setting details.
Table 16. Echo Cancellation Power-On Delay Setting on Main PCBA
SW6-1
Echo Cancellation Power-On Delay
Open* One
minute
Closed No
delay
N
OTES
:
1. Changes to this parameter take effect when cycling power.
2. *Indicates default position.
Manual Initiation of Echo Canceling
Echo cancellation can be manually initiated as described below.
Press and release push button PB1 on the Main PCBA three times. The push button must be pressed for at
least 0.25 second and no more than 2 seconds each time. The timing requirement is meant to prevent
accidental requests. If an error is made with the push-button timing, the sequence must be repeated from
the beginning.
The LEDs on the Main PCBA will indicate the progress of the echo canceling sequence. One column of
LEDs turns on after each push button press release until the sequence is started. Once the sequence is
started, those LEDs remain on, and a countdown timer is displayed on the remaining LEDs. The LEDs
turn OFF after the echo cancellation training sequence is complete.
Data Links between Line Extenders
The LE300 is equipped with two different data link types for connecting to another line extender. The two
data types are T1/E1 and Low Voltage Differential Signaling (LVDS). The type of data connection(s)
required is determined by the system architecture. It is possible to use both types at the same time to
achieve complex system architectures. Each data type, the intended use, and the applicable switch settings
are described below.