LEVEL SETTING AND INTERFACE ADJUSTMENTS
- continued
Adjusting DTMF Twist
The DTMF microphone generates two tones when any keypad button is pressed. The
following table illustrates the row tones and column tones generated by activating a
keypad button:
Column Tones (Hz)
1209
1336
1477
Row
697
1
2
3
Tones
770
4
5
6
(Hz)
852
7
8
9
941
*
0
#
The term "DTMF Twist" is the ratio between the level of the column tone and the row
tone generated by any keypad button. In application, the higher frequency (column)
tones are more readily attenuated than the lower frequency (row) tones, the high
frequency tones of any DTMF are
generated by the microphone at a slightly higher
level.
The 600L microphone is shipped with the proper DTMF twist required for most
applications, and this procedure should not be necessary.
Should a particular application require the DTMF twist to be tested or changed, the
following may be accomplished: (the temporary modification allows two keypad digits
to be pressed within a column or row - resulting in the generation of a single tone
applicable to that column or row):
(1) Cut the plating run on the bottom of the 600L printed circuit board at JP6.
(2) If installed, remove 600L microphone jumper JP4 (disables Burst Mode operation).
(3) Press two keys within a column (for high tones) or two keys within a row (for low
tones) while monitoring the transmitted tone level on a service monitor.
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