Comtech EF Data RCS10 - Manual (Page 218)

Principles of Operation RCS10 Redundant Communication System
Page 5-2 TM058 - Rev. 2.3
T1 (1.544 Mbps), E1 (2.048 Mbps), T2 (6.312 Mbps), and E2 (8.448 Mbps). Additionally, the line
code is selected when the interface type is selected with the exception that T1 may use B8ZS or
AMI as selected at the front panel.
The G.703 interface also contains two additional ports that can operate at T1 or E1 that provides a
4-port Drop & Insert interface. The ‘Send Data Out’ port provides an unaltered send data output that
can be used for daisy chaining additional systems. On the receive side, a T1 or E1 data stream can
be connected to the ‘Insert Data In’ port where received data will overwrite ‘dropped on’ the T1/E1
data stream. The modified T1/E1 data stream will then exit the modem out of the ‘Receive Data
Out’ port.
5.2 96 Kbps ESC Port
The ESC port (J10) sends and receives a 96 Kbps data stream formatted for IESS-308. Data is
routed between the BB Processor card framing unit and the external ESC channel unit. The
interface is designed for RS-422 balanced signal levels and contains Tx Data In, Rx Data Out, and
Tx Clock Out.
5.3 Terrestrial Loopback
The UIM module also provides for terrestrial loopback. For Tx Terr loopback, Tx Data, after passing
through the line interface is looped back to the Rx data line drivers. For RX Terr loopback, the
receive data from the satellite is looped back for retransmission to the satellite providing a far end
loopback. Tx/Rx loopback provides both loopbacks simultaneously.
5.4 Modem Status
The UIM provides several status indications that are controlled by the M&C processor.
Mod Fault - De-energized when any transmit side fault is detected.
Demod Fault - De-energized when any receive side fault is detected.
Common Fault - De-energized when any fault that is not explicitly a Tx or Rx fault such as an
M&C or power supply fault.
5.5 Baseband Processor Card
The Baseband processor card (BB Card) contains two major subsystems-- the Baseband
Processing System and the Monitor and Control Subsystem.
5.5.1 Baseband Processing
The baseband processor performs all of the functions required for an IBS/IDR Framing unit, a Reed-
Solomon Codec, and an E1/T1 Drop and Insert system. In addition, the baseband processing
section provides for Transmit clock selection and rate adaptation as well as a rate adapter and
Plesiochronous/Doppler (PD) Buffer in the receive direction. A multiplexer is also provided for the
SCT clock source for loop timing applications. The transmit and receive paths may be configured
independently under processor control.
5.5.2 Tx Baseband Processing
As shown in Figure 5-1, the Tx Data and clock enters the baseband processor, passes through a
rate adapting FIFO and enters the Framer/Drop processor. In closed-net mode, the data passes
through the framer unaltered. In IDR, IBS, and Drop and Insert modes the framer adds the
appropriate framing and ESC as defined in IESS-308 and 309. In D&I mode, the framer acquires the
terrestrial framing structure, E1 or T1, and synchronizes the drop processor. The drop processor
extracts the desired time slots from the terrestrial data stream and feeds these channels back to
the framer. The framer then places the ‘dropped’ terrestrial time slots into the desired satellite
channel slots. The data is then sent to the Reed-Solomon encoder.