XEV90 查看數據表（PDF） - Xecom
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XEV90 Datasheet PDF : 10 Pages
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Application Notes
Dialing:
The public switched telephone network permits tone and rotary
(pulse) dialing. The XEV90 supports both types of dialing.
Tone dialing requires an external signal source to provide the
dialing tones. Rotary dialing is accomplished by pulsing the
OH or Mute line on the XEV90.
Pulse Dialing: The XEV90 generates dialing pulses through
momentary closures of the switch-hook. (pulsing of the MUTE
signal can also be used to generate dialing pules) Each digit is
represented as a series of pulses, one pulse for a one to ten
pulses for a zero. The pulse rate in normally ten pulses per
second. (Some European countries require 20 pulses per
second.) The dialing pulses are asymmetrical. Consult with the
local country regulations for the required duty cycle. An
interdigit delay of at least one hundred milliseconds separates
the digits.
Tone Dialing: To tone dial the XEV90 seizes the line, OH
active. For each digit a unique DTMF, Dual Tone Multiple
Frequency, tone pair is placed across T1 and T2. The higher
frequency tone is always of greater magnitude than the lower
frequency tone. Transmit the tones for a minimum of 70
milliseconds, and leave a minimum of 70 milliseconds between
digits.
Insertion Loss: There is some loss of signal power as the
information signal passes through the XEV90. This "insertion"
loss should be taken into account when placing signals across
T1 and T2 for transmission. The typical insertion loss of the
XEV90 is 6 dBm.
Total Harmonic Distortion:
Total Harmonic Distortion is the most common measure of the
signal path quality provided by the DAA. The primary sources
of distortion in the DAA are the Telephone Line Transformer
and the Line Current Holding Circuit, although board layout
and other factors can introduce distortion.
Total Harmonic Distortion varies with frequency. The voice
band provided by the telephone line is limited to less than 4000
Hz. High speed modems such as 33.6 KBPS and 56KBPS
require virtually all of this bandwidth for signal transmission.
Even if the Total Harmonic Distortion of a device is very good
in the center portion of the spectrum, signal quality is compro-
mised if distortion greatly increases at the outer limits of the
voice band.
50
55
The table below shows the correct DTMF signal frequencies for
each digit.
60
Digit
Lower Tone
Upper Tone
1
697
1209
2
697
1336
3
697
1477
4
770
1209
5
770
1336
6
770
1477
7
852
1209
8
852
1336
9
852
1477
0
941
1336
*
941
1209
#
941
1477
Signal Levels: FCC Part 68 Rules set the allowable signal level
in the US for all signals placed on the telephone line other than
live voice. Other countries have similar regulations. Signal
levels are measured in dBm. Zero dBm is 1 milliwatt through a
600 ohm load.
65
70
75
80
85
50
100
200
500
1000
1500
2000
4000
90
Note: This chart represents the total harmonic distortion of the
complete DAA not just the telephone line transformer.
Distortion measurements of the transformer only will
show much lower distortion but do not account for
distortion from other sources.
XECOM
(7)
XEV90
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