Microwave Data Systems MDS 4310 Installation, Operation & Field Maintenance page 115

Once a loopback code has been entered, typing the
command results in a display of the code, followed by the letter
to indicated that it is "Installed." If a loopback code has not
I
been programmed, the letters
displayed, even if the module is present, since a valid code has
not been entered. Once the loopback code is entered and the
radio is shut down and re-powered up, the indicator will be I
for "Installed."
TESTING THE LOOPBACK CODE
This section presents three basic test options to verify that the transceiver is responding
properly to its programmed loopback code. Chapter 4—Field Tests and Adjustments, Test
Procedure covers procedures for programming a new loopback code.
The Remote Maintenance Module receives instructions over-the-air in the form of DTMF
signals from the system's master station. Outgoing data from the Remote Maintenance
Module is also modulated with DTMF signals.
Local Testing with a DTMF Encoder
A programmable DTMF encoder with an audio level output of –10 dBm can be attached to
Pin 22 of the
INTERFACE
system's master station. The radio's four digit loopback code can then be sent through J1-Pin
22 to the Remote Maintenance Module.
A properly decoded Loopback Code will key the radio and generate a series of DTMF signals
and a short, but steady, tone that is used by the master station for frequency and deviation
measurements. This basic response can be monitored on a communications service monitor.
Make sure to connect the
monitor before starting the test.
Local Testing with a Communications Service Monitor
Many communications service monitors are capable of providing sequential DTMF encoding
on their RF test signals. Connect the transceiver to the monitor's internal dummy load and
program the encoder to generate the four digit loopback code sequence as an on-channel
DTMF signal. Monitor the response from the transceiver as previously discussed.
Remote Testing with a "SMART" Master Station
With the radio installed in the system and the master station connected to a personal
computer running the MDS 2000 Diagnostic & Control System software, poll the remote
station using its loopback code. The appropriate diagnostic information should be displayed
on the PC screen. Review the software operating instructions for details.
TROUBLESHOOTING
If the Remote Maintenance Module does not respond to a four digit DTMF loopback code,
verify the installation and basic operation of the assembly by following this procedure.
1. Connect the HHT or ASCII terminal to the transceiver as previously described.
D-4
NOTE
connector J1 to emulate incoming DTMF polling signals from the
jack of the transceiver to the transmit input of the service
ANTENNA
APPENDIX D
for "Uninstalled" will be
UI
MDS 05-2415A01, Rev. A
L B C