MITEL MH89791 Datasheet
MH89791
CEPT PCM 30 Transmit Equalizer
Advance Information
Features
• Used with th e MH8 9790B
• Programmab le equ al ization for differen t line
lengths
• 6dB loop around circuit
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 doub l e thro w relay conne c ted to the tr an sformer
inputs and outputs shows how the transmit signal is
switched be tween the equalizer for normal operation,
ISSUE 4 May 1995
Pin Connections
1
TL
2
TL
3
TI
4
Ri
5
RL
6
RL
7
TxT
8
EIT
9
EA
10
L1
11
EB
12
EC
13
L2
TxR
EIR
SW
14
15
16
17
18
19
20
RCHT
RCLT
RCHR
RCLR
Ordering Info rmatio n -40°C to 85 °C
MH89791 20 Pin SIP Hybri d
and the 6dB pad for loop arou nd. Figur e 2 shows the
circuit description of the MH89791 while Figure 3
shows the switch settings for the Tx equalizer.
MH89790B
OUTA
OUTB
RxT
RxR
+12V
C2
L1
MH89791
•
•
1:
:0.5
1:
•
•
S1
S2
•
•
S3
S4
•
S5
S6
S7
EIT
EIR
EA
EB
EC
SW
RCLT
RCHT
RCLR
RCHR
Ti
Ri
TxT
TxR
C2 = .47µF
L1 = 33 µH
TL
RL
•
.8:
:1
.8:
•
Figure 1 - Connection Diagram
4-219
MH89791 Advance Information
240Ω
EQUALIZER
S5
•
3600pF
•
S4
•
•
468Ω
1600pF
•
6dB Pad
Tip O
Ring O
•
EiT TxT
60Ω
60Ω
Tip
••
Line
60Ω
•
120Ω
•
60Ω
•
60Ω
•
60Ω
Ring
Line
EiR TxR
•
60Ω
60Ω
•
60Ω
•
120 Ω
••
134.4Ω
6.8µH
S1
•
•
60Ω
60Ω
•
1600 pF
•
152. 4Ω
15µH
S3S2
60Ω
•
S6
•
468Ω
3600 pF
•
-=SWITCH OPENED
X=SWITCH CLOSED
4-220
•
S7
240Ω
•
Figure 2 - M H8979 1 Cir cuit Des crip tion
-
-
-
-
-
X
-
-
X
-
X
X
-
-
-
X
X
-
X
-
X
X
X
S1
X
--
S2
-X
S3
-
S4
-
S5
-
S6
-
S7
-
NO EQUALIZATION MAX. EQUALIZATION
-
-X
-X
-
-
-
-
-
-
-
X
-
-
-
X
-
-
X
X
-
INCREASING EQUALIZAT ION
Figure 3 - Swi tch Settin gs for Diffe rent Lev els of Eq ualization
-
-
X
-
X
-
X
X
-
-
X
X
X
X
--
X
X
X
X
X
-
-
X
X
X
X
X
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