Figure 3-7. Ds-1 Interface Block Diagram - Comtech EF Data SDM-650B Installation And Operation Manual

SDM-650B Satellite Modem
TX CLOCK
TX DATA
M
O
RX CLOCK
D
E
RX DATA
M
COMMON EQUIPMENT
MODULATOR
DEMODULATOR
DATA BUS TO M & C
The data to be transmitted by the modem is input on the SD lines. Jitter on the SD is
removed by a FIFO and clock recovery phase-locked loop. Data received and
demodulated by the modem is output on the RD lines.
The RD is driven from a pulse-shaper circuit which pre-equalizes the RD output to drive
up to 655 feet of ABAM cable. Refer to Table 3-3.
The DS-1 interface provides bi-directional loopback of the data at the DCE interface.
In loopback from the DTE side, SD is connected to RD.
In loopback from the modem side, the received demodulated data is routed back to the
modulator input for re-transmission.
Rev. 5
TO BUFFER
OPTIONS
DS-1
DEJITTER
TO BUFFER
OPTIONS
FAULT
RELAYS
CONTROL
LOGIC

Figure 3-7. DS-1 Interface Block Diagram

DS-1 LINE
RECEIVER/DRIVER
LOOPBACK CONTROL
EXTERNAL BUFFER CLOCK
TTL MODULATOR FAULT
TTL DEMODULATOR FAULT
Configuration
SD
T
RD
E
R
R
E
S
T
MC
R
I
A
L
3–21