A bit See ABCD bits.

A-law A companding algorithm used in E1 transmissions, primarily in Europe. Another algorithm, mu-law, is used in North America and Japan.

ABCD bits The signaling bits used to carry channel-associated signaling on digital CAS trunks and on MVIP signaling streams. The value that these bits take determines or indicates the state of the telephone channel. Many protocols do not use all four bits.

AG board See Alliance Generation board.

AG configuration file A text file containing configuration information for the AG boards in a system. When agmon runs, it configures the boards as described in this file.

agmon Utility program which reads a configuration file and uses it to load and monitor the AG hardware.

AIS See Alarm Indication Signal.

Alarm Indication Signal (AIS)
A T1 and E1 transmission alarm signal that replaces the normal traffic signal when a maintenance alarm indication has been activated. An AIS is a signal transmitted downstream indicating that an upstream failure has occurred. See also Blue Alarm.

Alliance Generation board (AG board)
A member of Natural MicroSystems' Alliance Generation family of telephony and voice processing hardware products.

Ally board Plug-in board that allows expansion of functionality for Alliance Generation boards.

Alternate Mark Inversion (AMI)
In T1 transmissions, the line-coding format where successive 1s (marks) are alternately sent with opposite polarity. AMI reduces crosstalk and allows robust low-energy transmissions.

AMI See Alternate Mark Inversion.

B bit See ABCD bits.

B channel See bearer channel.

B8ZS See Binary 8 Zero Substitution.

bearer channel (B channel)
A common channel signaling (CCS) term, meaning one of the timeslots on an E1 trunk or T1 trunk over which voice data and in-band signaling is passed. See also D channel.

Binary 8 Zero Substitution (B8ZS)
A technique used to maintain required ones density in T1 communications.

bipolar violation Successive "one" bits sent with the same polarity, disrupting the AMI pattern. Sometimes used for zero code suppression.

Blue Alarm One of the three alarms to indicate problems with T1 or E1 transmissions. The Blue Alarm occurs when two consecutive frames have fewer than three zeros in the data stream. A Blue Alarm sends 1s in all bits of all timeslots. Also known as the AIS (Alarm Indication Signal). See also Alarm Indication Signal, Red Alarm, Yellow Alarm.

C bit See ABCD bits.

CAS See Channel-Associated Signaling.

CCS See Common Channel Signaling.

CEPT Conference des administrations Europeenes des Postes et Telecommunications, a standards body that sets standards for services and interfaces.

channel An electronic communications path. In digital telephony, a channel usually refers to a separate connection carried on a digital trunk. Channel information is carried in timeslots, time-division multiplexed into a single continuous stream of information.

Channel-Associated Signaling (CAS)
A signaling system in which signaling information is sent for all channels at regular intervals, regardless of whether each channel's state changes or not. The information for each channel consists of a set of bits (called the ABCD bits). Whenever a channel's state changes, the ABCD bit pattern for that channel changes. On T1 trunks, this information is "buried" in the voice information using robbed-bit signaling. On E1 trunks, this signaling is carried in a separate channel.

Channel Service Unit (CSU)
A device connecting customer T1 equipment and a network line.

clock master The board that sources the clocks in an MVIP system.

clock slave A board that uses the clock master as a clock source.

codec COder-DECoder. A device that converts digital signals to analog, and vice versa.

Common Channel Signaling (CCS)
A signaling system in which packets of signaling information for a channel are sent when the channel's state changes (instead of signaling bits as in CAS). CCS information is sent in a dedicated channel, the data channel or D channel. Voice information is carried in bearer channels (B channels). ISDN is a common channel signaling system.

companding Compressing the amplitude of a signal in a non-linear fashion so the most characteristic elements of the signal are the most accurately represented. Mu-law and a-law are two companding algorithms.

CRC See Cyclic Redundancy Check.

CSU See Channel Service Unit.

Cyclic Redundancy Check (CRC)
A process used to check whether a block of data contains errors or not. The transmitting end computes a value based on the number of 1s in the data block, and sends the value with the data block. The receiving end makes the same calculation. If the values do not match, the receiving end requests the transmitting end to resend the block.

D3/D4 framing In T1 transmissions, a framing method in which a set of 12 frames, each consisting of 24 8-bit timeslots plus one framing bit, make up one M24 superframe. The framing bits are set or reset according to a pattern that repeats once per M24 superframe. The framing bit is carried in-band along with the encoded voice, using a technique called robbed-bit signaling.

D bit See ABCD bits.

D channel See data channel.

data channel (D channel)
A common channel signaling term, meaning the timeslot on a T1or E1 trunk in signaling information packets are passed.

Digital Signal Processor (DSP)
A microprocessor that is designed to perform the calculations required for voice processing.

Diva board Plug-in board that allows expansion of functionality for Alliance Generation boards.

DS-0 Digital Signal level 0. DS-0 is 64,000 bps.

DS-1 Digital Signal level 1. DS-1 is 1.544 Mbit/s in T1 transmissions, and 2.048 Mbit/s in E1 transmissions.

DSP See Digital Signal Processor.

DSX-1 A standard for the electrical and physical characteristics of a T1 cross-connect.

E & M Ear and Mouth; a telephone signaling system used between two switches that uses two wires called the E lead and the M lead. In analog E & M, the M lead of one switch is connected to the E lead of the other, and vice versa. In digital E & M signaling, a single bit is used to convey signaling states. A common mnemonic is that E stands for ear-lead and M for mouth-lead.

E1 A standard used in Europe for digital telephone carriers. E1 is similar to T1 but operates at 2.048 Mbit/s and has 32 channels instead of T1's 24.

e1stat A utility that lets you monitor the status of an E1 trunk, including alarm states, errored and failed seconds, bit error rate violations, framing slips and framer synchronization state.

e1test A utility that lets you debug and test an E1 application without connecting to a live trunk carrier. The utility lets you simulate an incoming call, monitor signaling, and interact with your application using DTMF or MFC-R2 tones.

ESF See Extended SuperFrame.

Extended SuperFrame (ESF)
A T1 framing method where frames are grouped in sets of 24, each frame consisting of 24 8-bit timeslots plus one extra bit. Every fourth extra bit is used for framing, and is set or reset according to a pattern that repeats once per extended superframe. All other extra bits are used for FDL or error checking information.

F bit See framing bit.

Facilities Data Link (FDL)
In T1 or E1 communications, extra bandwidth used for diagnostics data.

FDL See Facilities Data Link.

frame (T1 or E1) A portion of a PCM data stream that contains one binary data word, typically 8 bits, for each unidirectional channel. A frame usually will also contain control and synchronization bits and is 125 msec long.

Framing bit (F bit) In T1 framing, a single bit sent after each frame, to delineate the end of the frame and the beginning of the next one. After each frame, the F bit is set or reset according to a pattern that repeats at regular intervals, delineating M24 or ESF superframes.

full duplex Simultaneous two-way voice and two-way signal data transmission.

HDB3 See High-Density Bipolar 3.

HDLC controller A board component that processes the D channel information in each trunk frame.

High Density Bipolar 3 (HDB3)
A technique used to maintain required ones density in T1 communications

in-band Transmitted in the voice path. MF signaling is an in-band signaling method. See also out-of-band.

ISA Industry Standard Architecture; the de-facto bus card standard in the IBM-PC compatible world. Also known as the PC/AT bus.

ISDN Integrated Services Digital Network; a standard for providing voice and data telephone service with all-digital transmission and message-based out-of-band signaling.

jammed-bit ZCS A technique used to maintain required ones density in T1 communications.

line A logical telephone connection on which a call can take place.

loop start A method of signaling an off-hook or line seizure, where one end closes the loop circuit and the resulting current flow is detected by the switch at the other end.

loopback Connecting the input and outputs of a device locally. This configuration is typically used for testing purposes.

M24 superframe In D3/D4 framing, a set of 12 frames, each consisting of 24 8-bit timeslots plus one framing bit. The framing bit is set or reset according to a pattern that repeats once per M24 superframe.

MF Multi-Frequency; an in-band interoffice tone-based signaling method using pairs of frequencies from a set of six available frequencies.

MFC-R2 ITU standard line protocol for E1 lines and T1 lines using compelled MF tones and channel-associated signaling. Almost every country has a variant of this standard.

mu-law A companding algorithm used in T1 transmissions, primarily in North America and Japan. Another algorithm, a-law, is used in Europe.

multiframe In E1 transmissions, a group of 16 frames: 15 data frames and one synchronization frame.

multiplexing The transmission of two or more channels on a single physical circuit.

MVIP Multi-Vendor Integration Protocol; a PCM digital bus standard for integrating various board vendors. Facilitates software-controlled digital switching within the PC chassis. MVIP interconnects switching and telephony processing boards on a PC.

Network Facility Associated Signaling (NFAS)
An ISDN configuration with two or more T1 lines, where the D channel on one trunk carries the signaling for all B channels on all trunks. This leaves the 24^th channels on all other trunk lines free for use as B channels.

NFAS See Network Facility Associated Signaling.

off-hook The active state of a customer telephone circuit. The term is derived from old telephone sets where the receiver, when in use, was lifted from a hook attached to a switch. The opposite condition is on-hook.

ones density In T1 and E1 transmissions, the receiving end keeps in sync with the sending end based on the intervals at which 1s (discrete pulses of voltage) appear on the line. Large groups of consecutive zeroes (each zero represented by an absence of voltage) interfere with this timing. The sending end must maintain a certain density of "one" pulses on the line, using zero code suppression algorithms.

out-of-band Carried separately from voice information. ISDN signaling is sent out-of-band (in a D channel). See also in-band.

PCM See Pulse Code Modulation.

protocol The signaling scheme used on a trunk. Many different protocol standards, and variations of these standards, are in use around the world.

Pulse Code Modulation (PCM)
An analog-digital conversion method.

Pulsed E & M See E & M.

Red Alarm One of the three alarms to indicate problems with T1 or E1 transmissions. A Red Alarm is generated for a locally detected failure such as loss of synchronization for 2.5 seconds. See also Blue Alarm, Yellow Alarm.

robbed-bit signaling A T1 signaling method in which bits in the voice information in each channel are changed at regular intervals to convey the signaling bits. Since the intervals are widely spaced, sound quality in the channel is not compromised.

runfile A module of basic low-level software which an AG board requires to operate. The runfile for a board is specified in the AG configuration file. When agmon runs, it transfers the runfile from the host into on-board memory.

Sec8k clock Secondary 8 kHz clock, a secondary clock signal on the MVIP bus which can be used as a backup for the MVIP clock, or to synchronize MC1 bus communications.

showsig A utility which monitors the signals on all lines on a trunk simultaneously.

stream A group of timeslots. Typically, this term refers to the entire set of timeslots on a trunk, or the mapping of those timeslots onto the MVIP bus.

SW Utility A utility program for configuring and controlling MVIP boards. MVIP-90 compliant.

swish A utility program shipped with CT Access for configuring and controlling MVIP boards. MVIP-95 compliant.

SwitchPath A switching library provided by Natural MicroSystems for MVIP-90 compliant device drivers.

T1 A standard for telephone transmission that multiplexes up to 24 channels on a single 1.544 Mbps carrier.

t1test A utility that lets you debug and test a T1 application without connecting to a live trunk carrier. The utility lets you simulate an incoming call, monitor signaling, and interact with your application using DTMF or MFC-R2 tones.

t1stat A utility that lets you monitor the status of a T1 trunk, including alarm states, errored and failed seconds, bit error rate violations, framing slips and framer synchronization state.

TCP See Trunk Control Program.

TDM See Time Division Multiplexing.

Time Division Multiplexing (TDM)
A technique for transmitting a number of separate data, voice, and/or video signals simultaneously over one communications medium. The transmitting end sends a new piece of each signal at regular intervals, so the pieces together form a continuous stream of data. The receiving end samples this stream at the same intervals at which the transmitting end is placing data on the line, and puts each signal back together.

timeslot On a digital trunk and on the MVIP bus, information in each channel is time-division multiplexed into a single continuous stream of data. The interval in which each channel broadcasts is called a timeslot.

trunk A transmission channel connecting two switching machines.

Trunk Control Program (TCP)
A software module designed to run in an AG board's on-board memory, which interfaces a host application with an analog or digital trunk running a certain protocol. The TCP to use is specified in the AG configuration file, and is transferred to the AG board by agmon.

Yellow Alarm One of the three alarms to indicate problems with T1 or E1 transmissions. A Yellow Alarm signal is sent back toward the source of a failed transmit circuit in a transmission path. A Yellow Alarm sends zeros in bit two of all timeslots. See also Blue Alarm, Red Alarm.

ZCS See Zero Code Suppression.

Zero Code Suppression (ZCS)
The insertion of a "one" bit to prevent the transmission of eight or more consecutive "zero" bits. Used primarily with T1 or E1 facilities which require a minimum ones density.