9
2270 Fiber Optic Modem
Figure 1-1.
Front Panel
Mode/Rate
Switch
The rate setting determines what rate the modem will operate at if set to the Internal Clocking
Mode or the rate used when a modem set to the Slave Clocking Mode is set for local loopback.
The modes are:
External Clock
Internal Clock
Slave Clock
Flow Control
Alternate Loopback Functions
Switch positions 4, 5 and 6 select the clocking mode for the modem as described in Section 2.7
and shown in Table 2-A.
Switch position 7 selects whether the RTS input controls flow control through the modem (Open =
no flow control, Closed = flow control enabled). Refer to Section 4.8.1.
Switch position 8 selects the normal or alternate loopback mode as shown in Table 5-A of the
Troubleshooting section.
Indicator lights are provided for Power On, Optical Receive and Transmit data activity, Interface
Receive and Transmit data activity, and for Loopback On. All of these indicators are located on the
front panel, for both standalone and rack-mount versions.
The loopback switch on the front panel is used to activate the built-in system test or to select
either a Local or Remote loopback function. Use of this switch is outlined in Chapter 5, Trouble-
shooting.
The electrical interface connection and fiber optic connections are made at the rear of the modem.
The HI/LO optical power switch is also located there.
There is also a HI/LO switch for the optical receiver, used to select its sensitivity. Operating this
switch in the LO position may be necessary under certain low-loss conditions (refer to Section
1.9).