CANOGA PERKINS 2240 Fiber Optic Modem - Manual (Page 31)

31
Chapter 3
Mode and Rate Selection
3.1 Operating Mode, Data Rate Selection
The 2240 has eight clock operating modes: seven modes for synchronous data transmission and
one asynchronous mode. Each synchronous mode is characterized by one of three transmit
clock types: External Clock (clocked from customer's equipment), Internal Clock (modem
generates Tx clock and RX clock) and Slave Clock (transmit clock same as received from far-end
modem).
The operating mode is selected by setting three of the eight paddle-style switches (positions 5, 6
and 7) on the front panel (see Figure 3-1). Table 3-1 lists the modes and the switch positions. The
switch positions are numbered from left to right (1 to 8).
Front panel DIP switch Position 8 is now functional. It acts as an optical receiver frequency range
select. OPEN selects the new low range and CLOSED selects the original (or normal) operating
range. This switch should be in the CLOSED position except when the far end modem is
operating in Locked External Mode (Mode 7) and the far end modem's external clock frequency
falls into the LOW range (refer to Table 3-2).
Figure 3-1 2240 Front Panel Mode/Rate Switches
1 7 3 4 5 6 8 2
OPEN
CLOSED
RATE SWITCHES
MODE
RANGE
SELECT
(RATE 0 / MODE 7 / ORIGINAL RANGE SHOWN)