MSAN-108 Zarlink Semiconductor, Inc., MSAN-108 Datasheet - Page 2

• Manufacturer Part Number: MSAN-108
• Description: Applications of The MT8870 Integrated DTMF Receiver
• Manufacturer: Zarlink Semiconductor, Inc.

MSAN-108
A-46
a) Block diagram of a toll call restrictor. This could be implemented on a small pc board and installed
b) Block diagram of a simple tome to pulse converter to allow TOUCH-TONE dialing into a step-by-
in a telephone to disallow long distance calling.
step or crossbar exchange.
Telephone DTMF keypad matrix. Column H
reserved for special signalling.
LOW GROUP
TONES
DETECT CIRCUIT
LOOP CURRENT
L1 = 697 Hz
L2 = 770 Hz
L3 = 852 Hz
L4 = 941 Hz
Figure 1b - The Dual Tone Multifrequency (DTMF) Keypad
Figure 2 - Typical DTMF Receiver Applications
RECEIVER
H1 =
1209
MT8870
HIGH GROUP TONES
DTMF
Hz
1
4
7
*
LINE INTERFACE
RECEIVER
H2 =
1336
Hz
RESET
2
5
8
0
LOGIC
MT8870
DTMF
4
H3 =
1477
Hz
is normally not available on a telephone keypad and is
3
6
9
#
CENTRAL TELEPHONE SWITCHING OFFICE
H4 =
1633
Hz
A
B
C
D
DECODE
CIRCUIT
LOGIC
LINE SPLIT RELAY
CONTROL
LOGIC
DISABLE
LOGIC
DISCONNECT
DTMF signal not available on a standard
pushbutton telephone keypad
DRIVER
RELAY
RELAY
LEGEND :
LINE INTERFACE
MT4325
DIALER
PULSE
DETECTOR
RINGING
Application Note
TO TELEPHONE
& REGULATOR
STEP-BY-STEP
EXCHANGE
RECTIFIER
EXCHANGE
FILTER
V
TO
DD