CMX624P4 CMLMICRO [CML Microcircuits], CMX624P4 Datasheet - Page 15

• Manufacturer Part Number: CMX624P4
• Description: V.23 / Bell 202 Modem
• Manufacturer: CMLMICRO [CML Microcircuits]

V23 / Bell 202 Modem
1.6
1.6.1
A line interface circuit is needed to provide dc isolation between the modem and the line, to perform line
impedance termination, and to set the correct transmit and receive signal levels.
4-Wire Line Interface
Figure 8a shows an interface circuit for use with a 600
R10 and R15, while R11 and R13 should be selected to give the desired transmit and receive levels.
The gain of the receive input amplifier (R12 / R11) should be set to compensate for the loss of the input
transformer and the supply voltage.
Assuming transformer loss of about 1dB, R11 should be 91k
 2003 CML Microsystems Plc
Application Notes
Line Interface
R10
R11
R12
Note relay circuit, ac and dc loads and line protection not shown for clarity.
600
See text
100k
Figure 8a 4-Wire Line Interface Circuit
Resistors 1%, capacitors 20%.
R13
R14
R15
15
4-wire line. The line terminations are provided by
See text
100k
600
at 5.0V, or 130k
at 3.0V.
C10
C11
C12
C13
100nF
220pF
330pF
100nF
CMX624
D/624/7