User Manual

AS4000 Release3 and Release 4 Central
Terminal Installation and Commissioning
DLP-015
605-0000-432
Issue 1.3a Date 18th October 1999
Page 3 of 8
Figure 36. Power Level measurement Test Set-up
d) Restore power to the rack.
e) The single user output power is 21dB.
The TX output power level is maintained by a power control loop in the system.
For the power loop to work the CT RF card needs to generate greater than
+21.75dBm, this condition can be achieved by using the Sitespan to set two users in
service without any STs in operation. This forces the two modems (i.e. one modem
card) to stay in the high rate acquisition mode. Two users provide an output of 24 ±
1.0dBm.
f) For the CT to reach its nominal output power from zero using the control loop
would take a considerable length of time. To bypass this process, the power control
loop may be overridden using the Sitespan to set the TX power the control voltage.
g) Using the Sitespan select the RF Card view from the Shelf view.
h) Set the transmitter volts to 2.2 volts by using the Up/Down button. Observe that the
auto levelling sets the Output power to 24 ± 1.0dBm.
i) Record results
j) Switch off rack. by placing both breakers in the off position.
k) Ensure that the power Output is at steady level before setting up the RX gain
control.
5. Connecting Test CRU
The purpose of this test is to enable the RX sensitivity at the CT to be set to -98dBm
to within 1dB. This section provides details of the test set-up for the setting of the RX
gain control.
a) Set up the test equipment in preparation to connect to the shelf.
b) Programme the test CRU as follows with the same programming information as
that for the CRU at the ST associated with the modem under test.
• Remove the cover from the PSU
• Connect an MF or LD type telephone to the NTU
• To program the ST, depress the reset switch, (Type2 SW4 Type 4 SW2), in the
PSU for approximately 3 seconds. LED D8 will begin flashing to indicate the
CRU initialising and self test sequence. After approximately 10 sec, the CRU
initialising and self test sequence will be complete and the LED will be
extinguished. LED D9 will still be illuminated.
• Depress the Programming switch (Type2 SW3 Type 4 SW1). Lift the
telephone handset Off-Hook and wait for the 3 sec continuous “programming
start” tone of 1400 Hz, to be heard in the handset receiver.
• Enter the respective ST programming code on the telephone keypad, within 40
seconds of depressing the install switch. Should an incorrect programming
code be entered, an “incorrect code” tone shall be heard in the handset receiver,
which consists of 1400 Hz pulses for less than 1 sec on, and less than 1 sec off,
for a duration of 5 sec.