Data Sheet

AS2574B

Rev. 1

3

Jan. 1995

Pin Description Continued

Pin #

Pin Node

Description

24

HS

Hook switch input; active high with internal pull-down resistor. Debounce 25 ms.

25

Vss

Negative terminal of power supply.

26

TB

Tone burst output:

LS high

80 ms burst, 8 sec pause

MT high

80 ms burst, 2 sec pause

Only in speech mode

MT+LS high

80 ms burst, 2 sec pause

27

TONE

MF tone output.

An on chip reference voltage provides tone levels independent of the

supply voltage.

A dc path from TONE output is needed to accommodate an external voltage

divider for setting the appropriate tone level.

Frequencies:

Frequency (Hz)

Key Matrix (Hz)

Error (%)

697

row 1

770

row 2

852

row 3

941

row 4

1209

col. 1

≤ ± 0.7%

1336

col. 2

1477

col. 3

1633

see p. 7

28

Vdd

Positive terminal of power supply

RECALL

12

3

45

6

78

9

0

*

#

LS

LNR

M9

M1

M2

M3

M4

2ND

MUTE

M5

M6

M7

M8

COLUMN

12

3

456

1

2

3

4

5

The keyboard is arranged in a 5 x 6 contact matrix with single pole single throw

contacts (SPST).

Keyboard resistance: Ron < 5 k

Ω; Roff > 5 MΩ.

ENTER

MEM

M10

Enabled only

when off-hook

Enabled also

when ACP is

active (diode 5

inserted)

Enabled when

CD = high

In off-hook state all keys are

enabled (CD = high)

KeyboardLayout