Pots Connection; Going "Off-Hook; Auto-Answer - H Heuer Instruments UMDT51A User Manual

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
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
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.
LT51 User Manual
key to toggle from On-Hook to Off-Hook
key, followed by [f3] to toggle Auto-Answer between ON
Configuring the Tester
33