Calling Line Identifier with VMWI
CMX612
1.5
General Description
1.5.1 Mode Control Logic
The CMX612's operating mode and the source of the DET and IRQN outputs are determined by the logic
levels applied to the MODE 1 and MODE 2 input pins;
MODE 1 MODE 2
Mode
Tone Alert Detect
DET o/p from
Tone Alert Signal
Detection.
IRQN o/p from
0
0
Valid ‘off-hook’ CAS or
Ring or Line Polarity
Reversal Detection.
Ringing Signal present.
CAS tones present.
[1]
0
1
FSK Receive
FSK Level Detection.
FSK present.
FSK Data Retiming
or
Ring or Line Polarity
Reversal Detection.
Ringing Signal present.
Ring or Line Polarity
Reversal Detection.
Ringing Signal present.
1
1
0
1
'Zero-Power'
Ring or Line Polarity
Reversal Detection.
Ringing Signal present.
Dial Tone Signal Detection. Valid dial tone detected.
Both tones present.
Dial Tone Detect
[1]
If enabled.
In 'Zero-Power' mode, power is removed from all of the internal circuitry except for the Ring or Line
Polarity Reversal Detector and the DET and IRQN outputs.
1.5.2 Input Signal Amplifiers
These amplifiers can be used to convert the balanced FSK, Tone Alert and VMWI signals received over
the telephone line to an unbalanced signal of the correct amplitude for the FSK receiver, Tone Alert and
Dial Tone Detector circuits.
Figure 3a : Input Signal Amplifier, balanced input configuration
The design equations for this circuit are;
Differential voltage gain V
R6 = R7 = 470kW
R10 = 160kW
/ V(b-a) = R8/R6
AOP
R9 = R8 x R10 / (R8 - R10)
The target differential voltage gain depends on the expected signal levels between the A and B wires and
the CMX612's internal threshold levels, which are proportional to the supply voltage.
ã 2002 Consumer Microcircuits Limited
7
D/612/3
CMLMICRO [ CML MICROCIRCUITS ]
