Comtech EF Data OM20 - Manual (Page 46)

OM20 Universal Outdoor Modem OM20 Theory of Operation
MN-OM20– Revision 5 4–8
4.3.4 Modem Monitor Status
The modems M&C system is connected to most of the circuitry on any board contained in the
chassis. These connections provide status on the working condition of the circuitry as well as
providing the data required for the various measurements the modem provides. The M&C
processes this information and generates status indications as well as alarms when necessary.
Detailed status information is available via the modems various user interfaces (Web browser,
remote and terminal). A summary of this information can be connected to external equipment,
switches or alarms via the open collector and/or form-C fault connections
Form-C Contacts:
Two Form-C Relays under processor control are available on the OM20 connector J2
Mod Fault:
De-energized when any transmit side fault is detected.
Demod Fault:
De-energized when any receive side fault is detected.
Two Open Collector Faults are available on the OM20 connector J3 pins 10 &16
Mod Fault: Will sink up to 20 ma (maximum) until a transmit or common
fault is detected. Will not sink current if a fault is detected.
Demod Fault:
Will sink up to 20 ma (maximum) until a receive or common
fault is detected. Will not sink current if a fault is detected.
The open collector faults are intended for use in redundancy switch applications in order to
provide quick status indications.
4.4 Async Port / ES-ES Communications
This port is dedicated for ES-ES Communications supported by either RS232 or RS485 signal
levels. The baud rate and protocol can be selected from the Front Panel. The port may be
configured for a number of communications protocols. Overhead data to/from the UIM is routed
to/from the framer/deframer. This port is also used by SCC Framing for the in-band data.
4.5 Internal Clock
The time and date is kept in order to ‘time-tag’ system events. User can change the Internal
Clock via the front panel, Web Browser or Terminal ports.
4.6 Loopback Features (Terrestrial & IF)
The modem provides for a number of different loopbacks. The Loopback supported are:
 IF Loopback – Tx IF port is looped back to the Rx IF port
 TX Terrestrial Loopback - Tx Data port is looped back to the Rx Data port after the
interface driver/receiver. (prior to the framing unit)