Fig.8 Simplified proposal for electronic hook switch application of the UBA1702 in combination with a transmission and a hands-free circuit.

SPI

SDO

SDI

EHI

RPI

ROA

ROB

buzzer

RMI RV0

RV1

RV2

RF0

CLA CDA MSA ZPA

RTA

CD0

MSI

DPI

EHD MHD EHT

RV0

RV1

RV2

CE

T1

TONE

D1

BAT85

CVRR

22

µF

1.8

µF

1.8

µF

CVDD

22

µF

R1

620

Ω

VCC

DTMF VEE

SLPE

LN

TEA106x

3.58 MHz

XTAL1

XTAL2

VDD

VSS

VBB

SP0

VRR

VDD

VSS

VEE

PCD33xx

UBA1702

M1

BSP254

C1

100

µF

R9

20

Ω

QR

Loudspeaking

TEA1093

SUP

RIN

GND

LSP1

LSP2

100

nF

MHD: Mechanical Hook switch Detection

EHD: Electronic Hook switch Detection

EHT: Electronic Hook switch Take-over

CRMI

speaker-phone

button

D2

D3

cradle

BRIDGE

4 x BAS11

BRIDGE

4 x BAS11

a/b

b/a

BOD

BR211-240

D4

2.2 k

Ω

D5

3.3 V

MBE749

10 nF

Rprot

3.9

Ω