Using ISDN Codecs on Dedicated Digital Circuits
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Although the Nexus, Envoy and Matrix with ISDN Module contain an integral ISDN Terminal Adapter for direct connection to BRI ISDN circuits, they can also be used with Dedicated Digital Services such as a 56/64 circuit or a T1/E1 channel. Connection to these dedicated circuits will be made through an external DSU/CSU via the EIA530 data port on the Nexus or the external DCI port on the Envoy or Matrix ISDN Module. Check out our note on Adtran Terminal Equipment for some DSU/CSU options.
These units are capable of delivering 7.5 kHz bi-directional audio on a 56/64 kb/s circuit and 15 kHz bi-directional audio on a 128 kb/s circuit. In either case, they provide a 4800 baud ancillary data channel along with the wideband audio. This data channel may be used for remote control, for connection to remote monitoring equipment, to send text messaging between computers, etc.