Configuring the Tester
LT51 User Manual
33
POTS Connection
Connection to a POTS line must be made at the RTX terminals. Before making
any connection ensure the tester is set to
On-Hook.
This will ensure that the
input impedance is bridged and that no DC current will flow. In the
On-Hook
condition, the LT51 will respond to ring voltage by emitting an audible tone.
The current setting for
Hook Status
is displayed in the CONFIG bar along the
bottom of the LCD.
Going “Off-Hook”
To seize a line and go
Off-Hook
in response to ringing, or to initiate a new
connection:
press the key to toggle from
On-Hook
to
Off-Hook
When going
Off-Hook,
the speaker volume is set to 50% and the Speaker-Phone
is active. See the section on Volume Control for more information.
When in the
Off-Hook
condition, and the Interface is set to
RTX
(ie. the
Transmitter output is selected to appear at the RTX terminals), the input
impedance is terminated to sink loop current and thereby seize the line. To
ensure the correct AC impedance is presented at the RTX terminals, a special
hybrid circuit is deployed providing accurate TX levels over the selected
frequency span.
The following restrictions apply when
Off-Hook:
-
PSD modes are not available.
-
the RTX terminals are fixed on
a-b
.
Auto-Answer*
To aid in automatic testing, the LT51 can be configured to automatically seize
the line on detection of the second applied ringing signal. When measuring the
RMS of Ring Voltage or any AC Voltage, this feature should be disabled:
Press the key, followed by [f3] to toggle
Auto-Answer
between
ON
and
OFF.
When the LT51 has auto-answered an incoming call, a timer is started. This
timer is reset whenever one of the following occurs; a button is pressed, a
command from a MASTER is received (if this LT51 is a SLAVE) or a command
over the PC interface is received. If the timer is not reset within 1-2 minutes of
the last action, the line is disconnected and the LT51 goes
On-Hook
.
*Not available when the protection voltage is 60V. See specifications.
Summary of Contents for UMDT51A
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