Glossary

Glossary

Term Description

ADSL Asymmetric Digital Subscriber Line is a digital data service with differing transmit and receive (upstream and downstream) data rates. It is designed to be a cost effective, high speed data service for Small Office/Home Office (SOHO) applications.

Baud See bps.

bandwidth The frequency of a data signal. The higher the frequency (bandwidth), the higher the data rate and consequently the greater amount of data that can be carried. Also used to describe the portion of a given data transport resource that is being used; i.e., two DS3's use two thirds of the total bandwidth of an OC-3.

bps Bits per second.

Central Office (CO) The building and associated equipment through which telephone voice and data circuits are switched and/or transported.

CO switch A digital computer that switches (routes) phone calls. All signals are encoded into digital form. The bits of each signal are placed into a datastream at particular time slots and then pulled out of the stream at appropriate time slots that correspond with the desired destination circuit. This is referred to as Time Division Multiplexing.

dry circuit A plain metallic loop with no electrical energy present.

fiber optics The process of transmitting infrared and visible light frequencies through a low loss glass fiber (for some purposes, plastic may be used). Light sources include laser and Light Emitting Diode (LED). NOTE: Protect your eyes! NEVER LOOK INTO FIBER ENDS. There can be enough energy emitted from them to damage your eye(s)!

Gateway A connection through which LANs may interconnect to other LANs (or WANs) or to connect to the Internet.

Gbps Billions of bits (Gigabits) per second.

Hub A network device that allows users to interconnect several devices such as personal computers, servers, printers and gateway devices to form a LAN.

ISDN Integrated Services Digital Network. A telephony standard set forth as the foundation for digital data services to be provided by telephone companies to homes and businesses. Available in two formats, BRI (basic rate interface) is 144,000 bps and PRI (primary rate interface) is 1,544,000 bps (same rate as T1/ DS1 rate).

LAN Local Area Network is a localized collection of computing and data devices forming a data network.

Mbps Millions of bits (Megabits) per second.

megahertz Millions of cycles per second.

mode An independent light path through a fiber.

off hook When the telephone instrument hand set is lifted from its cradle.

optical fiber - multimode An optical waveguide (or fiber) in which the light travels in multiple modes. This fiber has a larger core/cladding diameter of typically 62.5-125.0 micrometers. This fiber exhibits higher loss than single-mode.

optical fiber - single mode An optical waveguide (or fiber) in which the light travels in one mode. This fiber has a smaller core diameter of typically 8.3-9.5 micrometers. This fiber exhibits lower loss than multimode.

ringing current Electrical signal of approximately 90 volts at 20 milliamps, 20 Hertz alternating current that causes a telephone instrument to ring.

SONET Synchronous Optical Network is an ANSI standard. [The international equivalent of SONET, standardized by the ITU-T, is called Synchronous Digital Hierarchy (SDH).]

STS-1 Synchronous Transport Signal level 1 is the basic signal rate of SONET, is 51.84 Mbps.

talk battery Approximately 48 volts DC that is applied to a completed circuit to provide power for the telephone sets to operate.

telco Telephone operating entity.

WAN Wide Area Networks are a collection of LANs in geographically diverse locations interconnected so as to appear to the users to be one seamless network.

wet circuit A plain metallic loop with electrical energy present. Various uses may include powering far end equipment or for "sealing current" used to prevent relay contact corrosion and loss of continuity through said contacts.

Table 1

North American telephone system equipment data rates:

DS-1 1.544 Mbps (T1)

DS-1C 3.152 Mbps (T1C)

DS-2 6.312 Mbps (T2—historical info only, no longer used)

DS-3 44.736 Mbps (T3)

DS-4 274.176 Mbps (T4)

Optical Carrier (SONET OC) rates (with STS-1 signal):

OC-1 51.84 Mbps can transport 1 ea. DS-3 28 ea. DS-1 672 voice channels

OC-3 155.52 Mbps can transport 3 ea. DS-3 84 ea. DS-1 2016 voice channels

OC-12 622.08 Mbps can transport 12 ea. DS-3 336 ea. DS-1 8064 voice channels

OC-48 2488.32 Mbps can transport 48 ea. DS-3 1344 ea. DS-1 32256 voice channels

OC-192 9953.28 Mbps can transport 192 ea. DS-3 5376 ea. DS-1 129024 voice channels

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Term	Description
ADSL	Asymmetric Digital Subscriber Line is a digital data service with differing transmit and receive (upstream and downstream) data rates. It is designed to be a cost effective, high speed data service for Small Office/Home Office (SOHO) applications.
Baud	See bps.
bandwidth	The frequency of a data signal. The higher the frequency (bandwidth), the higher the data rate and consequently the greater amount of data that can be carried. Also used to describe the portion of a given data transport resource that is being used; i.e., two DS3's use two thirds of the total bandwidth of an OC-3.
bps	Bits per second.
Central Office (CO)	The building and associated equipment through which telephone voice and data circuits are switched and/or transported.
CO switch	A digital computer that switches (routes) phone calls. All signals are encoded into digital form. The bits of each signal are placed into a datastream at particular time slots and then pulled out of the stream at appropriate time slots that correspond with the desired destination circuit. This is referred to as Time Division Multiplexing.
dry circuit	A plain metallic loop with no electrical energy present.
fiber optics	The process of transmitting infrared and visible light frequencies through a low loss glass fiber (for some purposes, plastic may be used). Light sources include laser and Light Emitting Diode (LED). NOTE: Protect your eyes! NEVER LOOK INTO FIBER ENDS. There can be enough energy emitted from them to damage your eye(s)!
Gateway	A connection through which LANs may interconnect to other LANs (or WANs) or to connect to the Internet.
Gbps	Billions of bits (Gigabits) per second.
Hub	A network device that allows users to interconnect several devices such as personal computers, servers, printers and gateway devices to form a LAN.
ISDN	Integrated Services Digital Network. A telephony standard set forth as the foundation for digital data services to be provided by telephone companies to homes and businesses. Available in two formats, BRI (basic rate interface) is 144,000 bps and PRI (primary rate interface) is 1,544,000 bps (same rate as T1/ DS1 rate).
LAN	Local Area Network is a localized collection of computing and data devices forming a data network.
Mbps	Millions of bits (Megabits) per second.
megahertz	Millions of cycles per second.
mode	An independent light path through a fiber.
off hook	When the telephone instrument hand set is lifted from its cradle.
optical fiber - multimode	An optical waveguide (or fiber) in which the light travels in multiple modes. This fiber has a larger core/cladding diameter of typically 62.5-125.0 micrometers. This fiber exhibits higher loss than single-mode.
optical fiber - single mode	An optical waveguide (or fiber) in which the light travels in one mode. This fiber has a smaller core diameter of typically 8.3-9.5 micrometers. This fiber exhibits lower loss than multimode.
ringing current	Electrical signal of approximately 90 volts at 20 milliamps, 20 Hertz alternating current that causes a telephone instrument to ring.
SONET	Synchronous Optical Network is an ANSI standard. [The international equivalent of SONET, standardized by the ITU-T, is called Synchronous Digital Hierarchy (SDH).]
STS-1	Synchronous Transport Signal level 1 is the basic signal rate of SONET, is 51.84 Mbps.
talk battery	Approximately 48 volts DC that is applied to a completed circuit to provide power for the telephone sets to operate.
telco	Telephone operating entity.
WAN	Wide Area Networks are a collection of LANs in geographically diverse locations interconnected so as to appear to the users to be one seamless network.
wet circuit	A plain metallic loop with electrical energy present. Various uses may include powering far end equipment or for "sealing current" used to prevent relay contact corrosion and loss of continuity through said contacts.

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