|The ITA-703, Rate and Interface
Converter, enables connection of low speed DTE equipment to a G.703
co-directional interface, for interconnection with the PCM network. Rate
conversion is performed according to CCITT I.463 (V.110) and I.460
standards, enabling access to ISDN terminal adapters.
The ITA-703 operates synchronously or
asynchronously at V.24 rates up to 19,200 bps. For async rates of 600
bps and higher, the async to sync conversion technique is compatible
with CCITT V.14. For async rates lower than 600 bps, the ITA-703
operates synchronously at 19,200 bps and over-samples the async data.
Coupling to the G.703 4-wire interface line is
through isolation transformers which, in conjunction with other
circuitry, protect against AC or DC overvoltages.
The ITA-703 supports a full duplex transmission
rate of 64 kbps for a transmission distance of up to 800 meters ( 1/2
mile) from the G.703 equipment. The high speed transmit timing source is
strap-selectable for either :
- Recovered clock from the G.703 interface;
- External timing from the V.24 interface;
- Internal timing.
Diagnostic features include local loopback and
remote digital loopback in compliance with CCITT V.54. The operator at
either end of the line may test both units and the line when in the
digital loopback mode. Loopback can be controlled either from the front
panel push-buttons or via pins 18 and 21 of the V.24/RS-232 interface.
V.24 configuration parameters (such as bit rate,
bit length and sync/async) can be selected at each ITA-703, or else
centrally at the "master" ITA-703. Parameters are downline loaded from
the "master" to the "slave" ITA-703.
The control signals RTE and DTR are passed
end-to-end to DCD and DSR respectively, in compliance with CCITT I.463
(V.110). Alternatively DSR can be set separately to be continuously ON.
The ITA-703 is available as a desk-top unit or as
a card for insertion in a 19" card-nest. The card-nest can carry up to
fourteen cards. Special hardware for mounting the stand-alone units in a
19" rack can be ordered separately (see Ordering). This hardware enables
installation of either one or two units side-by-side. Unit height is
only 1U (1.75"), requiring minimal rack space.