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| KX-T2388
CIRCUIT OPERATIONS
Note:
The circuit diagram may be modified at any time with the development of new technology.
MITELEPHONE
LINE
INTERFACE
When the hook switch $101 is ON (off-hook), the circuit is closed, and current is supplied to the base of Q2 via
the diode bridge D5~D8, and Q2 is ON > Q1 is ON (OFF-HOOK condition).
Q1 and Q2 are the dial palse generating circuits, and are driven by the CPU (IC1), when the collector of Q4 is high logic
level > Q3 is ON — Q2 is OFF and Q1 is OFF. (break)
if port 8is LOW — Q3 is OFF > Q2 is ON > Q1 is ON. (make)
The ring signal is outputted from pin 8 of IC3, and its volume is adjusted in 3 steps (H-L-OFF) by Ringer SW then
impressed on the ceramic sound generator, and so is generated.
Rove eaninntesiens
Bell sensitivity adjustment
R3, C4 .........0..
Bell frequency setting fH1, fH2
R4,C3
.........06.
Repeat frequency setting fL
fH1, fH2, fL are derived from the following formulas:
1
1
fH1 m-----n->e-noennaerorenennannennereceeenacecsenewsen =982Hz
[a
=16.7 Hz
1.515 x R3 x C4
1.234
x R4 x C3
R3 = 82k
C4 = 0.0082 pF
R4 = 220k
C3 = 0.22 uF
fH2e1.24 x fH1=1218 Hz
'
The following shows the waveform of the tone ringing IC output:
ic3
@®pin
fH1
fH2
fL
fH1 = 982 Hz
fH2 = 1218 Hz
fL = 16.7 Hz
Circuit Diagram (for Handset)
1c1@BREAK
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