®
MH88632
Central Office Interface Circuit
Preliminary Information
Features
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Loop start and ground start capabilities
Transformerless 2-4 wire conversion
Programmable transmit/receive gain with 0dB
defaults
Programmable input impedance with 600Ω and
900Ω defaults
Programmable network balance with 600Ω,
900Ω, and AT&T compromise default
One loop start & two ground start relay drivers
Line state detection outputs
Forward loop, reverse loop, ring ground, tip
ground, ringing voltage
+5V operation
On-hook audio reception (to accommodate ANI)
ISSUE 5
April 1995
Ordering Information
MH88632
40 Pin SIL Package
0°C to 70°C
Description
The Mitel MH88632 Central Office Trunk Interface
circuit provides a complete audio and signalling link
between audio switching equipment and a central
office. The functions provided by the MH88632
include 2-4 Wire Hybrid conversion, programmable
transmit and receive gains, programmable line
impedance and programmable network balance. The
device is fabricated using thick film hybrid
technology which incorporates various technologies
for optimum circuit design and very high reliability.
Applications
I
nterface to Central Office for:
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PBX
Key Telephone System
Channel bank
Voice Mail
Terminal Equipment
Digital Loop Carrier
RING TIP
VDD
VEE
AGND
RV FL RL RG TG
Status
Detection
XLA
XLB
XLC
XLD
LRC
LRD
BRC
BRD
GRC
GRD
Loop
Termination
Receive
Gain
2-4 Wire Hybrid
Transmit
Gain
RX
GRX1
GRX0
TX
GTX1
GTX0
Loop Relay
Driver
Bias Relay
Driver
Ring Ground
Driver
Impedance
Matching
Network
Balance
VRLY RGND
Z1 Z2 Z600 Z900 NS N1 N2 NATT
Figure 1 - Functional Block Diagram
2-235
MITEL [ MITEL NETWORKS CORPORATION ]
