Specifications

Appendix C IR-G.703/CO Interface Module FOM-40 Installation and Operation Manual
C-2 Selecting the IR-G.703/CO Timing
C.2 Selecting the IR-G.703/CO Timing
The IR-G.703/CO interface module can operate with EXT or INT/RCV timing to
match the clock reference of the FOM-40 modem. The clock selection is made
using the JP1 jumper located on the module board (see Figure C-2).
JP1
INT/RCV
EXT
Figure C-2. JP1 Location on the IR-G.703/CO Board
EXT Timing
The EXT clock is used in applications where the G.703 network provides system
timing. The IR-G.703/CO module has an internal buffer that compensates for the
phase delay introduced into the system by the line delay between the two
modems. The buffer is an 8-bit FIFO connected as shown in Figure C-3.
If the FOM-40 modem is set to external timing, configure the IR-G.703/CO
module to the EXT clock.
Timing Source
TX Data
TX
TX
RX
RX
RX Data
G.703
Codirectional
64 kbps Network
FIFO
EXT Clock Mode RCV Clock Mode
Clock In
Clock
Out
Modem A Modem B
Clock
Recovery
Data
Data
CLK
Clock
Recovery
FIFO
IR-G.703 Module
Clock
Recovery
Figure C-3. IR-G.703/CO EXT Timing