CMX624D5 CML Microcircuits, CMX624D5 Datasheet - Page 7

• Manufacturer Part Number: CMX624D5
• Description: V.23/Bell 202 modem
• Manufacturer: CML Microcircuits

V23 / Bell 202 Modem
1.5.2
This amplifier, with suitable external components, is used to adjust the received signal to the correct amplitude
for the FSK receiver and Energy Detect circuits and may also form part of a 2-wire or 4-wire hybrid circuit; see
Section 1.6.1.
1.5.3
This block includes a bandpass filter whose characteristics are set by bits 4 and 5 of the FSK MODE Register
according to the receive operating mode (Call Progress, 75/150bps FSK or 1200bps FSK). It is used to
attenuate out of band noise and interfering signals, especially the locally generated transmit FSK signal which
could otherwise interfere with the received FSK signal when the modem is operating in 2-wire duplex mode.
When receiving 1200bps FSK data an optional equaliser section, enabled by setting bit 6 of the FSK MODE
Register, compensates for one-half of the ETS Test Line 1 characteristics shown in Figure 3b.
2001 Consumer Microcircuits Limited
Rx Input Amplifier
Receive Filter and Equaliser
Figure 3b ETS 300 114 Test Line 1 Characteristics (Normalised)
dB
ms
dB
5
4
3
2
1
0
-10
-20
-30
-40
Figure 3a Rx Frequency Responses with Line Interface,
0
0
100
500
see section 1.6.1 (equaliser disabled)
1000
1500
7
2000
1000
Hz
Hz
2500
dB wrt 800Hz
ms wrt 1700Hz
3000
1200bps
75/150 bps
Call Progress
3500
10000
4000
CMX624
D/624/6