Canoga Perkins 2240, Руководство пользователя, Страница: 77 / 106

2240 Fiber Optic Modem
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A wire wrap header (J3) provides the means to interconnect these resources
together with the standard modem transmit and receive circuits to perform the
intended function. Figure 4-5 illustrates how the resources are tied into the J3
header. Specific applications are satisfied by wire wrap connections between
appropriate pins.
Four pre-wrapped headers are provided with the interface. These implement
the most common applications. See Figures 4-7, 4-9,4-11 and 4-13. Numer-
ous other configurations are possible by different wired versions of the header,
P3. The four versions included are identified by part number labels affixed to
the underside of the header. The version included in the socket as shipped is
P/N 610030-001 (see Figure 4-13).
The P53 can be used to interface with encryption devices on the BLACK side
where modems act as the network and supply clocking in a synchronous
configuration, or to the RED (clear) side of a data encryption (KG) equipment.
In the RED side application, the interface acts as the "tail-circuit adapter"
device. This configuration allows the modem to accept two synchronous
clocks (typically, DCE devices only accept one): one for transmit (external
clock) and one for receive (FIFO input clock).
Another common application is with systems that communicate over geosyn-
chronous satellites. In this application, the FIFO is used to make up for clock
drift (Doppler shift) caused by the satellite's elliptical orbit around the earth.