P300H
P300 Series Modem Installation and Operating Handbook
Page 20
Two Audio ESC ports (4 wire 600 , +7 to -16dBm). In addition to normal IDR ESC operation
these ports may also be used in IBS modes to generate a 64kbps IBS carrier comprising just the
two 32kbps ADPCM audio channels, or a 128kbps IBS carrier comprising 64kbps data (from the
main data interface of the modem) plus the two 32kbps ADPCM audio channels. This is an
emulation of the most popular modes of the P1348/P1448 voice/data mux card used often in
SNG applications.
An RS232/RS422/RS485 Port for sync/async ESC traffic, this port
replaces
the shared
ESC/Aux access via the Async ESC connector on the main unit. Used to provide access to the
8kbps synchronous IDR ESC channel. If the Async ESC feature is available (standard on P300-
IBS and above) then Async access to the 8kbps channel is also available. Again if the Async
ESC feature is available this port also provides the high rate Async ESC on IBS/SMS or Closed
Net Plus ESC services
An RS232/RS422 port for sync/async Aux traffic, this port
replaces
the shared ESC/Aux access
via the Async ESC connector on the main unit. The Aux port provides 32 or 64kbps access to
the IDR overhead in place of one or both of the IDR 32kbps ADPCM Audio ESC channels. If the
IBS/SMS feature is available then this port may be configured to provide either the IBS `low rate
INTELSAT
oversampled
ESC facility`, or a higher rate
synchronous
channel within the IBS/SMS
overhead.
Pinout details are provided in Appendix B.
Terrestrial Interface Connectors
The P300 provides as standard both 25 pin EIA530 and 37 pin RS449 female DCE connectors. NOTE
that these are simply wired in parallel and you should not connect both simultaneously. The electrical
interface is front panel selectable to be RS422, V.35, and RS232. Normally for RS232 operation the
EIA530 connector would be used (which is standard 25 pin RS232 compatible) and for RS422 the 37 pin
RS449 connector. The old style 34 pin `Winchester` connector favoured for V.35 interfaces has poor
EMC performance and so could not be incorporated whilst maintaining CE compliance. If this style of
connector is required then an external adaptor cable must be used.
If the
G.703 option
is fitted, then
in addition
to RS422/V.35/RS232, G.703 is also available as a
software selectable interface standard. T1 (1544kbps) G.703 is a balanced 100 signal, and is provided
on both `D` type connectors when G.703 is selected from the front panel. When the E1 (2048kbps)
G.703 option is fitted then in addition to providing support for the balanced 120 signal on both `D` type
connectors an additional pair of BNC connectors are provided to accept the unbalanced 75 interface
standard. THE SELECTION BETWEEN 75 and 120 IS MADE BY A SWITCH ON THE E1 G.703
OPTION not by software. As with the 25/37 pin connectors, do not connect signals to both the BNC and
`D` type connectors simultaneously.
In addition a switch on both the T1 and E1 G.703 options controls
what happens to the G.703 port
when power is removed
. Either the G.703 ports can be set to go high impedance (used in 1:1
redundancy operation) or it can be configured to loop the G.703 input back to the output (typically used
when Drop/Insert is in operation and the same PCM bearer is cascaded through several modems).
Again (as it affects what happens when power is removed) this is SET BY A SWITCH ON THE CARD
not by software.
Finally, for special customer requirements it is possible to fit different interfaces to this port. Note that
UNLIKE PREVIOUS PRODUCTS the interface does NOT simply unplug
. Instead it is constructed as
part of the main modem, and requires `snapping off` and a connector to be soldered in place before a
replacement card can be fitted.
Standby LED
This LED mirrors the front panel standby LED, so that from the rear of the equipment the operator can
tell if the carrier is off, or more importantly which unit of a 1:1 pair is the offline unit.
