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P300H P300 Series Modem Installation and Operating Handbook Page 19
Rx IF input
This connector is a BNC female and can be used as either a 50
or 75 input. The allowable signal level
of the desired carrier at the input of the modem is from -60dBm to -30dBm (P310: -70dBm to -20dBm). A
level of -45dBm is recommended. The maximum composite power level that should be applied to this port
is 30dB above the desired carrier, up to a maximum of 0dBm (P310: Composite +35dBc to max of -
10dBm).
Alarms and AGC connector
This is a 15 pin male 'D' type connector that provides access to the three form `C' relay contacts that
indicate alarm conditions. Also provided on this port if the Monitor/AGC option is fitted is an uncommitted
analog output which by default provides an AGC output, but which may be selected via the front panel to
provide other user requested signals (eg Eb/No, Rx IF offset frequency, or other uses implemented as
required). The alarm relays have the following definitions:
Unit Fault:A unit fault exists, i.e. an equipment failure.
Traffic Prompt: A Tx or Rx traffic fault exists.
Deferred alarm: One of the following conditions exists:
The receive BER is greater than the user defined threshold.
The receive Eb/No is lower than the user defined threshold.
Buffer slips are more frequent than the user set threshold.
A Backward alarm is being received from either the satellite or terrestrial
ports.
Full pinout details are provided in Appendix B. The alarm relay functions can be changed, See `Relay
Mode` in appendix E.
Async ESC connector
This 15 pin `D` female connector provides a superset of the features found previously on the front panel
circular 8 pin `din` connector. It includes an RS232 serial port for the loading or revised internal software
from a PC or the printing of the units traffic log to a serial printer / PC terminal emulator. If the Monitor/AGC
option is fitted it provides I, Q, and symbol clock outputs to monitor the receive constellation (in order to view
received signal quality on an oscilloscope). When the IDR option IS NOT fitted, it provides an
RS232/RS422/RS485 asynchronous port for either the high rate Async ESC facility (for IBS/SMS or Closed
Net Plus ESC services) or the IBS/SMS `low rate INTELSAT oversampled ESC facility` (which is configured
as the Aux data channel on the modem). When the IDR option IS fitted, separate ports for the ESC and Aux
channels on the IDR card are activated, and ESC/Aux access on this async port is disabled. Finally, this
connector also provides the port for an RS422 compatible Station Clock (see the Station Clock paragraph
on the previous page).
Tx IF output
This connector is a BNC female and can be used as either a 50
or 75 output. The output power level
can be varied from 0dBm to -25dBm on 0.1dB steps from the front panel (P310: -5dBm to -30dBm).
ESC & Aux connector
This connector is fitted as part of the IDR option (Standard on P300-IDR & P300-TCM), it provides access
to:
Four backward alarm form `c` outputs, and the 4 backward alarm inputs, together with a Rx
summary alarm signal for direct connection to the backward alarm inputs. Note that these can be
used both in IDR modes, and (if the IBS and `Custom Features` features are available) a custom
IBS mode which allows four backward alarms for low rate IBS multidestinational carriers.
Two Audio ESC ports (4 wire 600 , +7 to -16dBm). In addition to normal IDR ESC operation these
ports may also be used in IBS modes to generate a 64kbps IBS carrier comprising just the two
32kbps ADPCM audio channels, or a 128kbps IBS carrier comprising 64kbps data (from the main
data interface of the modem) plus the two 32kbps ADPCM audio channels. This is an emulation