Multi-Tech Systems MTA128ST-USB - Manual (Page 90)

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MultiModemISDN User Guide
MTA128ST-USB
O
OHCI (OpenHCI): Open Host Controller Interface
Specification for USB. All transfers on the USB are
initiated by the host system’s host controller. The host
controller is responsible for controlling traffic on the USB
and can be appropriately programmed to transfer data to
and from USB devices. This is typically a PCI device that
can be programmed to run a given schedule of transfers
on the USB and bus master the results into memory for
processing by the host software. There are currently two
standards for host controllers: OpenHCI (OHCI or Open
Host Controller Interface) and UHCI (Universal Host
Controller Interface). Both these standards define register
level interfaces of the host controller to PCI bus. Bandwidth
allocation over the USB is software managed and is done
by the programming of the host controller.
off-hook—The condition of a device that has accessed a
phone line (with or without using the line). In modem use,
this is equivalent to a telephone handset being picked up.
Dialing and transmission are allowed, but incoming calls
are not answered.
on-demand dialing—A cost-saving feature of ISDN that
sets up, transfers, and then closes a call only when the
ISDN device detects a data packet addressed to the
remote network, but will not perform setup/transfers of just
administrative (non-user data) packets.
out-of-band signaling—A system that uses a separate
communications channel or frequency outside the voice
band for signaling. Modern systems use a separate
channel, either TDM or virtual. SS7 uses messages for
signaling that are carried on signaling links distinct from
voice channels. ISDN uses messages for signaling that are
carried on the
D-channel distinct from the voice carried on the B-
channels. Frame Relay and ATM use messages that are
carried on a separate virtual connection reserved for
signaling.
on-hook—The condition of a device which has not
accessed a phone line. In modem use, this is equivalent to
a telephone handset that has not been picked up. In other
words, it can receive an incoming call.
P
packet data—Packet-mode calls.
packet mode—The switching of chunks of information for
different users using statistical multiplexing to send them
over the same transmission facility. ISDN packet mode
capabilities are based on the ITU-TSS Recommendation
X.25 procedures.
parity bit—An extra bit attached to each byte of
synchronous data used to detect errors in transmission.
PBX (private branch exchange)—A telephone exchange
located on the customer’s premises. The PBX provides a
circuit switching facility for tlephone extension lines within
the building, and access to the public telephone network.
See also exchange.
P-channel (PCHAN)—The ISDN physical channel
identification; contrast logical channel or virtual channel.
PDN (public data network)—A packet-switched network
that is available to the public for individual (subscriber) use.
Typically, controlled by a government or a national
monopoly.
Plug and Play (PnP): A technology for configuring I/O
devices to use non-conflicting resources in a host.
Resources managed by Plug and Play include I/O address
ranges, memory address ranges, IRQs, and DMA
channels.
port—A location for input or output data exchange.
Computers, muxes, etc. have ports for various purposes.
PPP (Point to Point Protocol)—A protocol that lets a
computer user access a TCP/IP address using an ISDN
terminal adapter or a high-speed modem over a standard
telephone line.
PRI (Primary Rate Interface)—One
of two forms of ISDN service. PRI provides 23 64 Kbps B-
channels for video, voice or data, and one 64 Kbps D-
channel for control information. Usually used to connect
high-cpacity CPE, such as PBXs, to the network. Also
called 23B+D in the U.S. and 30B+D in Europe.) See also
ISDN and BRI.
primitive—An abstract representation of interaction
accross the access points indicating that information is
being passed between the service user and the service
provider. The OSI Reference Model defines four types of
primitives: Request, Indication, Response and Confirm.
PSTN (public switched telephone network)—The group of
circuit-switching voice carriers, which are commonly used
as analog data communications services. A worldwide
public voice telephone network that is used as a
telecommunications medium for the transmission of voice,
data and other information.
pulse dialing—One of two methods of dialing a telephone,
usually associated with rotary-dial phones. Compare with
tone dialing.
PVC (permanent virtual circuit)—A connection between two
endpoints dedicated to a single user. In ISDN, PVCs are
established by network administration and are held for as
long as the user subscribes to the service.
Q
Q.921—The ITU-T recommendation for user-network
interface layer 2 specifications for D-channel signaling.
Similar to LAPD. See also ISDN.
Q.931—The ITU-T recommendation for user-network
interface layer 3 specifications for D-channel signalling.
See also ISDN.
R
R reference point—Establishes the boundary between
non-ISDN compatible equipment (TE-2) and the IDN
network. TAs are used to convert the communication
protocol used by the non-ISDN termnials to the desired
BRI or PRI protocol. Non-ISDN (TE2) terminal equipment
connects to IDN at the R-Reference point with a TA. (This
interface may follow the RS232 or V.35 specification.) Also
called the R interface. (Contrast S reference point.)
RAM (random access memory)—A computer’s primary
workspace. All data must be stored in RAM (even for a
short while), before software can use the processor to
manipulate the data. Before a PC can do anything useful it
must move programs from disk to RAM. When you turn it
off, all information in RAM is lost.