wave.
The signal flow to the line is as follows.
Pin 11 of IC1 R37 Q9 Q3 Q1 Tel Line.
The DTMF signal is sent to the line via the following path. Q9 and Q3 is an amplifier which is used
to output the signal to line.
Shown below is the signal flow used to output the DTMF signal from the handset as a monitor
tone when a dial key is pressed.
Pin 11 of IC1 R48 C33 Q7 C18 Handset Speaker.
The signal combination and frequency corresponding to each dial key is shown on next page.
Tone Frequencies
High Group
Low Group
H1 H2 H3
L1 1 2 3
L2 4 5 6
L3 7 8 9
L4 0 #
Low Group Frequencies High Group
L1 697 Hz ± 1.5% H1 1209 Hz ±
L2 770 Hz ± 1.5% H2 1336 Hz ±
L3 852 Hz ± 1.5% H3 1477 Hz ±
L4 941 Hz ± 1.5% ----- -----
11
To Next Page
Loading...
