User guide

ASCOM USER GUIDE
High Speed Base Band Modems
21
5.1 QUICK GUIDE TO BASIC FAULT FINDING
No. Symptom Possible Fault Corrective Action
1 Power LED does Blown fuse. Replace fuse in mains lead.
not light.
2 Power LED lights Contrast adjustment is Check the screen contrast adjustment as
but LCD screen wrongly set. described in section 6.1.
information is
either missing or
of poor visibility.
3 Modems do not Configuration of Check configuration as detailed in section 4.3.
synchronise. modems incorrect.
If modems set to independent mode check that
the configuration of each end matches.
Check that settings have not reverted to
default (see section 5.2).
Lines not correctly Check that line pair(s) are correctly connected
connected. together (not crossed).
Line attenuation or Select a lower data rate.
line noise too high.
External timing Check external timing signal quality,
signal incorrect. and cable assembly.
Check configuration (Section 4.3.).
Internal fault. Return unit for repair.
Verify by running self
test. (Also reported with
line rate / pairs = 0).
4 Modems Line attenuation or Select a lower data rate.
synchronised but line noise too high.
high error rate.
External timing Check external timing signal frequency
signal incorrect. and quality.
Short line. Switch transmit power to 7.5dBm setting.
5 Modems Test loop active. Ensure no tests active at either modem.
synchronise but
Interface control Check control lines relevant to interface and if
no data transfer. lines incorrect. necessary set the to “on”. e.g for V.28 circuits
108 and 105 should be on for data transfer.
If the lines are not used a range of clamping
operations are possible. See section 6.4.
5 TROUBLESHOOTING
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20 ASCOM USER GUIDE
High Speed Base Band Modems
4.3.2.1 Setting External Timing
• Select the CONFIG MENU.
• Press the SCROLL DOWN button four times. One of the following messages will appear:
• Press the Select Button until the required timing mode is displayed.
• Press the PROG button to implement your setting. The modem is now configured for
external timing.
4.3.3 Desktop unit to Ascom rack system
The AM Rack (and MSM Rack) is a high-density 19” DIN41494 rack that allows 12 card style
modems to be housed together. The rack modems can be configured either as MASTER or
SLAVE units, though it is usual to have the rack based modems as MASTER units and the
desktop unit as SLAVE. Configuration of your desktop modem to work with a rack unit is as
described in sections 4.3.1.1 and 4.3.1.2.
4.3.4 Desktop unit to Ascom AM70 Multiplexer
The AM70 is a primary level flexible multiplexer housed in a 19” rack. It is possible to integrate
High Speed modems into the AM70 network by using HIRAC cards. The HIRAC card can
support five 512K channels and is always configured as a MASTER unit. To link your modem
to a HIRAC you must configure it as a SLAVE unit this is described in section 4.3.1.1.
This arrangement also allows the interface options to be downloaded, (in addition to the
configuration settings).
For details of the configuration settings at the multiplexer, please refer to the AM70
documentation.