MH88422
Preliminary Information
14
TIP
13
RLS
MH88422
VX
6
Audio Output
VR
TIP
11
C2
D1
10
9
RING
RING
1
VDD
AGND
TXIN
TF
RVLC
7
Audio Input
4
Ring Voltage & Loop
Current Detect Output
LC
2
3
Loop Control Input
+
C1
+5V
NOTES:
1) C1: 10µF, 6V Tantalum
2) C2: 0.1µF, 250V (Typical Value)
3) D1: 180VDC Foldback Diode, e.g. TISP4180, TISP5180
4) VX and VR are biased at 2.5V, therefore, coupling capacitors
may be required depending on application.
Calls are set up and cleared in this mode by the
external controller. It turns on the loop via Loop
Control, dialling by pulsing loop control (or via
DTMF tones) and clearing down by turning Loop
Control off.
Figure 3 - Typical Application Circuit
14
TIP
R6
TIP
K1a
13
RLS
11
MH88422
VX
6
Audio Output
7
TF
D1
RING
Line
Relay
Input
K1b
C2
K1
9
RING
10
TXIN
R2
Internal
dummy
Ringer
Resistor
VR
Audio Input
RVLC
4
Ring Voltage & Loop
Current Detect Output
3
LC
VDD
AGND
2
+
C1
Loop Control Input
1
NOTES
:
R2 & C2 form a dummy ringer, where R2 is on the hybrid and C2 must be fitted by the customer.
To initate a manual call, lift the handset. The RVLC pin will indicate that the line has been seized by the monitor phone.
The required number is then dialled and the connections established. During this phase the Loop Control
input should be turned ON to ensure that when the relay K1 is operated and the monitor phone removed from the line loop
current is still maintained. On receipt of the correct progress tones the external controller should control the data transmission
and clear down the call when it is completed by turning the Loop Control OFF. For applications in some countries such as
Germany the MH88422 can not be used with an optional telephone but may still be used in a combined telephone/fax machine.
1) C1: 10µF, 6V Tantalum
2) C2: 0.47µF, 100V
+5V
K1b
3) D1: 180VDC Foldback Diode, e.g. TISP4180, TISP5180
4) VX and VR are biased at 2.5V, therefore, coupling capacitors
may be required depending on application.
5) R6 adjust the monitor phone detect sensitivity typically set to 200 ohms for 5mA limit on the
-1 variant and 75 ohms on the -3 variant.
6) K1b is added to remove the dummy ringer when using a combined phone on the-1 variant
and is not required for all other variants.
Figure 4 - Typical Application Circuit with Dummy Ringer and Monitor Phone
2-28
MITEL [ MITEL NETWORKS CORPORATION ]
