XE014J Ver la hoja de datos (PDF) - Xecom
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XE014J Datasheet PDF : 9 Pages
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XE014J Applications Notes (continued)
Dialing:
The public switched telephone network permits tone and
rotary dialing. The XE014J supports both types. Tone
dialing requires an external signal source to provide the
dialing tones to the XE014J. Rotary dialing is accom-
plished by pulsing the OH line on the XE014J.
Tone Dialing: When tone dialing, the XE014J seizes
the line, OH active. The DTMF, Dual Tone Multiple
Frequency, dialing tones are placed across T1 and T2.
Each digit uses a unique tone pair. The higher frequency
tone is always larger than the lower frequency one.
Transmit the tones for a minimum of 70 milliseconds,
and leave a minimum of 70 milliseconds between digits.
The chart below shows the correct frequencies for each
digit.
Some countries, notably Italy, require low impedance
values during pulse dialing. For these countries, the
XE014J provides a Mute switch to generate the dialing
pulses rather than OH. .
Signal Levels:
FCC Part 68 Rules set the allowable level of all signals
placed on the telephone line other than live voice. For
the most common certification type, a "Permissive"
connection, data, fax, synthesized voice and other infor-
mation signals are limited to -9 dBm. Zero dBm is 1
milliwatt through a 600 ohm load. The rules provide
for a different limit for DTMF, Dual Tone Multiple
Frequency, tones. The combined power of the two tones
may be as high as 0 dBm with the higher frequency tone
at least 2 dBm larger than the lower tone.
Digit
1
2
3
4
5
6
7
8
9
0
*
#
Lower Tone
697
697
697
770
770
770
852
852
852
941
941
941
Upper Tone
1209
1336
1477
1209
1336
1477
1209
1336
1477
1336
1209
1477
Pulse Dialing: The XE014J generates dialing pulses
through momentary closures of the switch-hook. Each
digit is dialed as a series of pulses, one pulse for the digit
one, ten pulses for a zero. The pulse rate is ten pulses
per second. The dialing pulses are asymmetrical. The
correct duty cycle varies from country to country. An
interdigit delay of at least one hundred milliseconds is
required to separate the digits.
Insertion Loss: There is some loss of signal power as
the information signal passes through the XE014J. This
"insertion" loss should be taken into account when
placing signals across T1 and T2 for transmission. The
typical insertion loss of the XE014J is 3 dB.
2/4 Wire Conversion:
Full Duplex communications over a two-wire telephone
line requires that transmit and receive signal share the
available bandwidth. The two-to-four wire convertor
separates these signals at the host interface. Many
modem analog front end chips incorporate an internal 2/
4 wire convertor making it unnecessary to provide one in
the DAA.
If you are using the XE014J for an application other than
a modem, such as voice processing, or your modem
analog front end does not provide the 2/4 wire convertor,
you will need to provide a discrete 2/4 wire convertor.
Figure 6 shows a simple 2/4 wire convertor circuit.
XECOM
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XE014J
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