ADTRAN DSU III TDM Manual page 124

Appendix F. Glossary
DDS
digital data service also called digital data system. A private line digital ser-
vice, for transmitting data end-to-end at speeds of 2.4, 4.8, 9.6, and 56 kbps
and in some cases 19.2, 38.4, or 64 kbps. The systems can use central hub
offices for obtaining test access, bridging legs of multipoint circuits, and
cross connecting equipment. DDS is offered on an inter-LATA basis by
AT&T and on an intra-LATA basis by the Bell operating companies.
DDS II
Same as DDS but provides a slower speed secondary channel in addition to
the main DDS channel.
DDS Stress Patterns 1-4
A series of test patterns designed to test DDS circuits. Each pattern is
designed to stress the DDS circuit in a particular manner to assure its reli-
ability.
DSU
See data service unit.
DSU loopback
A telco initiated test which loops the DSU back to the telco and is used to
test the DDS circuit as well as the DSU/CSU.
DTE
data terminal equipment. In the EIA-232C standard specification, the EIA-
232C is connected between the DCE and a DTE. The main difference
between the DCE and the DTE is that pins two and three are reversed.
DTE to loop rate matching
A feature designed into ADTRAN DSU/CSU products that allows slower
DTE devices to communicate over 56/64 kbps digital circuits.
DTR-dialing
data terminal ready. A control signal sent from the DTE to the DCE that
indicates the DTE is powered on and ready to communicate. DTR dialing
allows a DSU/CSU to dial a predetermined number when DTR goes high.
F-4 DSU III TDM User Manual 61200063L1-20