MC33219A Datasheet, PDF (25/28 Pages) Motorola, Inc – Voice Switched Speakerphone

Freescale SMeCm33i2c1o9Anductor, Inc.
GLOSSARY
Attenuation – A decrease in magnitude of a
communication signal, usually expressed in dB.
Bandwidth – The range of information carrying
frequencies of a communication system.
Battery – The voltage which provides the loop current to
the telephone from the CO. The name is derived from the fact
that COs have always used batteries, in conjunction with AC
power, to provide this voltage.
C–Message Filter – A frequency weighting which
evaluates the effects of noise on a typical subscriber’s
system.
Central Office – Abbreviated CO, it is a main telephone
office, usually within of a few miles of its subscribers, that
houses switching gear for interconnection within its
exchange area, and to the rest of the telephone system. A
CO can handle up to 10,000 subscriber numbers.
CO – See Central Office.
CODEC – Coder/Decoder – In the Central Office, it
converts the transmit signal to digital, and converts the digital
receive signal to analog.
dB – A power or voltage measurement unit, referred to
another power or voltage. It is generally computed as:
10 x log (P1/P2)
for power measurements, and
20 x log(V1/V2)
for voltage measurements.
dBm – An indication of signal power. 1.0 mW across
600 Ω, or 0.775 Vrms, is defined as 0 dBm. Any other voltage
level is converted to dBm by:
dBm = 20 x log (Vrms/0.775), or
dBm = [20 x log (Vrms)] + 2.22.
dBmp – Indicates dBm measurement using a
psophometric weighting filter.
dBrn – Indicates a dBm measurement relative to 1.0 pW
power level into 600 Ω. Generally used for noise
measurements, 0 dBrn = – 90 dBm.
dBrnC – Indicates a dBrn measurement using a
C–message weighting filter.
DTMF – Dual Tone MultiFrequency. It is the “tone dialing”
system based on outputting two non–harmonic related
frequencies simultaneously to identify the number dialed.
Eight frequencies have been assigned to the four rows and
four columns of a keypad.
Four Wire Circuit – The portion of a telephone, or central
office, which operates on two pairs of wires. One pair is for
the Transmit path, and one pair is for the Receive path.
Full Duplex – A transmission system which permits
communication in both directions simultaneously. The
standard handset telephone system is full duplex.
Gain – The change in signal amplitude (increase or
decrease) after passing through an amplifier or other circuit
stage. Usually expressed in dB, an increase is a positive
number and a decrease is a negative number.
Half Duplex – A transmission system which permits
communication in one direction at a time. CB radios, with
“push–to–talk” switches, and voice activated speakerphones
are half duplex.
Hookswitch – A switch within the telephone which
connects the telephone circuit to the subscriber loop. The
name is derived from old telephones where the switch was
activated by lifting the receiver off and onto a hook on the side
of the phone.
Hybrid – A two–to–four wire converter.
Idle Channel Noise – Residual background noise when
transmit and receive signals are absent.
Line Card – The printed circuit board and circuitry in the
CO or PBX which connects to the subscriber’s phone line. A
line card may hold circuitry for one subscriber or a number of
subscribers.
Longitudinal Balance – The ability of the telephone
circuit to reject longitudinal signals on Tip and Ring.
Longitudinal Signals – Common mode signals.
Loop – The loop formed by the two subscriber wires (Tip
and Ring) connected to the telephone at one end, and the
central office (or PBX) at the other end. Generally it is a
floating system, not referred to ground, or AC power.
Loop Current – The DC current which flows through the
subscriber loop. It is typically provided by the central office or
PBX, and ranges from 20–120 mA.
Mute – Reducing the level of an audio signal, generally so
that it is inaudible. Partial muting is used in some
applications.
OFF Hook – The condition when the telephone is
connected to the phone system, permitting the loop current to
flow. The central office detects the DC current as an
indication that the phone is busy.
ON Hook – The condition when the telephone is
disconnected from the phone system, and no DC loop
current flows. The central office regards an ON hook phone
as available for ringing.
PABX – Private Automatic Branch Exchange. In effect, a
miniature central office; it is a customer owned switching
system servicing the phones within a facility, such as an
office building. A portion of the PABX connects to the Bell (or
other local) telephone system.
Power Supply Rejection Ratio – The ability of a circuit to
reject outputting noise or ripple, which is present on the
power supply lines. PSRR is usually expressed in dB.
Protection, Primary – Usually consisting of carbon
blocks or gas discharge tubes, it absorbs the bulk of a
lightning induced transient on the phone line by clamping the
voltages to less than ±1500 V.
Protection, Secondary – Usually located within the
telephone, it protects the phone circuit from transient surges.
Typically, it must be capable of clamping a ±1.5 kV surge of
1.0 ms duration.
Pulse Dialing – A dialing system whereby the loop current
is interrupted a number of times in quick succession. The
number of interruptions corresponds to the number dialed,
and the interruption rate is typically 10 per second. The old
rotary phones and many new pushbutton phones use pulse
dialing.
Receive Path – Within the telephone, it is the speech
path from the phone line (Tip and Ring) towards the
receiver or speaker.
REN – Ringer Equivalence Number. An indication of the
impedance (or loading factor) of a telephone bell or ringer
circuit. An REN of 1.0 equals ≈ 8.0 kΩ. The Bell system
typically permits a maximum of 5.0 REN (1.6 kΩ) on an
individual subscriber line. A minimum REN of 0.2 (40 kΩ) is
required by the Bell system.
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