Glossary E-17
speech detection
Determining the presence or absence of speech for Digital Speech Interpolation. Performed in
either the CDP card or VDP card in an IPX node.
split clock
A data clocking configuration where the timing for the transmit data is obtained from one source
(e.g. user device) and the timing for the receive data is obtained from another source (e.g. IPX
switch).
Status Enquiry
A message transmitted by a FR NNI port requesting an updated status from the attached foreign
network. This message is used as a heartbeat to detect when a port has failed.
StrataBus
On the BPX switch, contains crosspoint wiring used to carry ATM trunk data between both the
network interface and service interface modules and the crosspoint switch as well as providing
control, clock, and communications.
subrate data
Multiple low-speed data circuits carried in a single DS0 timeslot.
superrate data
Single high-speed data circuit carried in multiple DS0 timeslots.
SCR (Sustained Cell Rate)
Long term limit on the rate a connection can sustain.
SVC (switched virtual circuit)
A virtual circuit that is dynamically established on demand and torn down when transmission is
complete. SVS do not need to reserve any network resources when they are not in use. Called a
switched virtual connection in ATM terminology. Compare with PVC.
system bus
A two-part IPX data bus. One part carries system commands between the PCC all other IPX
cards; the other carries time division multiplexed data.
T
T1
The standard US. multiplexed 24-channel voice/data digital span line. Operates at a data rate of
1.544 Mbps.
T3
Transmission service at DS3 rate of 44.736 Mbps.
TBE (Transient Buffer Exposure)
The negotiated number of cells that the network would prefer to limit the source to send during
the start-up period.
TDM (time division multiplexing)
The process of combining several communication channels by dividing a channel into time
increments and assigning each channel to a timeslot.
