®
MH88400
Line Interface Circuit
Preliminary Information
Features
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FAX and Modem interface
Suitable for V.29 FAX & V.22 bis Data
Allows caller identification
Variants match German, UK, 600
Ω
& 900Ω
network impedances
Isolation circuitry conforms to international PTT
requirements
Transformerless 2-4 Wire conversion
Loop start operation
Pulse and DTMF operation
Accommodates external monitor phone
Line state detection outputs:
-loop current/ringing outputs
-monitor phone switch hook
Single +5V operation
ISSUE 1
April 1995
Ordering Information
MH88400-1 14 Pin DIL Package
MH88400-2 14 Pin DIL Package
MH88400-3 14 Pin DIL Package
0°C to 70°C
Description
The Mitel MH88400 Line Interface Circuit provides a
complete audio and signalling link between audio
equipment and central office. The functions provided
by the MH88400 include 2-4 Wire conversion, loop
seizure, external monitor phone switch hook status
and ringing voltage and loop current detection. The
device is fabricated as a thick film hybrid which
incorporates various technologies for optimum circuit
design, high voltage isolation and very high
reliability.
Variants are provided to meet German (-1) and UK
(-3) and general 600Ω (-2) line impedance (see
section on Line Impedances).
Isolation Barrier
Power
Supply
•
Applications
Interface to Central Office for:
• DAA
• Modem
• FAX
• Answering Machine
• Terminal Equipment
Transformer
Isolation
VDD
AGND
TIP
RING
Active
Termination
Opto-
Isolation
Opto-
Isolation
Audio
Buffer
Logic Input
Buffer
VR
LC
TXIN
TF
RLS
Audio Input
Buffer
Input
Buffer
Opto-
Isolation
Opto-
Isolation
Audio
Buffer
Ring & Loop
Buffer
Switch Hook
Buffer
VX
RVLC
PHS
Opto-
Isolation
SHK
NETWORK CONNECTIONS
USER CONNECTIONS
Figure 1 - Functional Block Diagram
2-11