®
MH89791
CEPT PCM 30 Transmit Equalizer
Advance Information
Features
•
•
•
Used with the MH89790B
Programmable equalization for different line
lengths
6dB loop around circuit
TL
TL
TI
Ri
RL
RL
TxT
EIT
EA
L1
EB
EC
L2
RCHT
RCLT
TxR
EIR
SW
RCHR
RCLR
ISSUE 4
May 1995
Pin Connections
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
Description
The MH89791 is a programmable network for use
with a PCM 30 line interface, specifically the
MH89790B on The ISDN EXPRESS™ Card. The
MH89791 contains transmit equalizer and a 6 dB
pad, for external loop around, with 120Ω input and
output impedances. It is fabricated in thick film
hybrid technology and is 2 inches high by 0.5 inches
wide. The MH89791 is designed to interface to 22
gauge/.6 mm twisted pair. Figure 1 shows how the
MH89791 is connected to the transmit side of a PCM
30 interface.
The seven switches control the
distance settings of the equalizer. Ti, Ri, TL, and RL
are the inputs and outputs of the 6 dB pad. The 4
pole double throw relay connected to the transformer
inputs and outputs shows how the transmit signal is
switched between the equalizer for normal operation,
MH89790B
OUTA
+12V
L1
C2
1:
OUTB
Ordering Information -40°C to 85°C
MH89791
20 Pin SIP Hybrid
and the 6dB pad for loop around. Figure 2 shows the
circuit description of the MH89791 while Figure 3
shows the switch settings for the Tx equalizer.
MH89791
•
1:
:0.5
•
•
S1
S2
EIT
EIR
TxT
TxR
EA
EB
EC
SW
RCLT
RCHT
RCLR
RCHR
Ti
Ri
TL
RL
C2 = .47µF
L1 = 33
µH
•
•
•
•
S3
S4
S5
S6
S7
RxT
.8:
:1
.8:
RxR
•
•
Figure 1 - Connection Diagram
4-219
MITEL [ MITEL NETWORKS CORPORATION ]
