Glossary - HP 27140A Hardware Reference Manual

Glossary
Baud
ccrrr
Conditioned Telephone Lines
Console, System
Duplex Transmission
EIA
EPROM
Modem
6-2 Reference
Unit of signalling speed expressed
as
the number of signal event changes
per second. It is a function of the modulation scheme and of the transmis-
sion carrier. It is rarely the same as "bits per second".
Comite Consultatif Intemational
de
Telegraphe et
de
Telephone -- Interna-
tional Telegraphy and Telephony Consultative Committee. A part of the
International Telecommunications Union of the United Nations. Respon-
sible for establishing communications protocols for the Post, Telegraph
and Telephone (PTT) ministries of most countries except the U.S.A. and
Canada. (See also EIA)
Using additional equipment, telephone companies can guarantee certain
levels of transmission quality. This service'is called conditioning, and for
AT&T, in the U.S.A., there are seven types or levels. These are graded
"basic", Cl through CS, and Dl. Conditioning affects several characteris-
tics of transmission, and each level affects different characteristics dif-
ferently, or not at all. There are also various combinations of conditioning
which may be required or desirable for your application. Conditioning
may be applied only to leased circuits.
The terminal which is used by the computer operator to control the run-
ning of the computer.
Duplex transmission is the simultaneous, bi-directional transmission of
data between two points. It is frequently called "Pull Duplex".
Electrical Industry Association. An association of electrical manufac-
turers who have agreed to adhere to standards for designing and produc-
ing communications equipment. The most common for modems is the
RS-232-C standard to which the HP 27140A was designed. (See also
CCITT)
Erasable, Programmable, Read Only Memory. A semiconductor memory
device which cannot be altered by the user. Access to memory addresses
which hold program code for execution by the Central Processing Unit
(CPU) is completely random. It is available instantly on power up, since it
is not power dependent (that is, it is non-volatile). EPROMs can be
erased, usually by exposure to ultraviolet light sources.
MOdulator/DEModulator. A device which takes a digital signal from the
computer or the terminal device and modulates it into an analog electrical
signal. This new, modulated signal may now be passed over telecom-
munications networks, and with a suitable modem located at the distant·
end, it can be demodulated or translated into the original digital signal.