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CHAPTER 4: Operation
REGISTER
NUMBER
REGISTER FUNCTION
S22
Option bit mapped register
Bit 0
Determines speaker volume
Bit 1
Determines speaker volume
Bit 1
Bit 0
Function
0
0
Low speaker volume
0
1
Low speaker volume
1
0
Medium speaker volume —
default
1
1
High speaker volume
Bit 2
Determines speaker status
Bit 3
Determines speaker status
Bit 3
Bit 2
Function
0
0
Speaker always off
0
1
On until carrier is detected —
default
1
0
Speaker always on
1
1
Same as “01”, except off for dialing
Bits 4-6 Determines response messages
Bit 6
Bit 5
Bit 6
Function
0
0
0
Basic message set
1
0
0
Extended with connect 1200, connect 2400
1
0
1
Extended with “No dial tone”
1
1
0
Extended with “Busy”
1
1
1
Extended with all messages
—
default
Bit 7
Determines Off Hook/On Hook (Make/Break) Ratio for
Pulse dialing
Bit 7
Ration
0
39/61 (USA and Canada);
default
1
33/67 (UK and Hong Kong)
