tea1065t NXP Semiconductors, tea1065t Datasheet - Page 13

• Manufacturer Part Number: tea1065t
• Description: Versatile Telephone Transmission Circuit With Dialler Interface
• Manufacturer: NXP Semiconductors

Philips Semiconductors
The maximum hook-off current then becomes:
I
(R9a
where V
Side-tone suppression
Suppression of the transmitted signal in the earpiece is
obtained by the anti-sidetone network comprising R1//Z
R2, R3, R9 and Z
is obtained when the following conditions are fulfilled:
a) R9
b) k = R3
c) Z
The scale factor k is chosen to meet the compatibility with
a standard capacitor from the E6 or E12 range for Z
In practice Z
line type. Therefore, the value chosen for Z
an average line length giving satisfactory sidetone
suppression with long and short times. The suppression
March 1994
hook-off
handbook, full pagewidth
Versatile telephone transmission circuit with
dialler interface
bal
= k
= V
R9b
R2 = R1
Z
is the Zener voltage of diode D5 (see Fig.18).
Z
(R8
/R1
line
Z
line
R1)/(R1
varies considerably with the line length and
bal
V
R9)/(R2
(R3
BE
(see Fig.18). Maximum compensation
Fig.14 Example of line current shape in pulse dialling mode (see also Fig.18).
R9b)
R8)
R9)
I hook-off
I line
0
0
hook-off
bal
should be for
speech mode
bal.
line
,
13
pulse dialling mode
also depends on the accuracy of the match between
Z
Example
With k = 1, R1 = 619 , R9 = 20
impedance represented by 270
calculation results in:
The anti-sidetone network for the TEA1060 family, shown
in Fig.15, attenuates the signal received from the line by
32 dB before it enters the receiving amplifier. The
attenuation is almost constant over the whole
audio-frequency range.
Note
More information on the balancing of the anti-sidetone
bridges can be obtained in our publication “Versatile
speech transmission ICs for electronic telephone sets” ,
order number 9398 341 10011.
bal
R2 = 130
R3 = 3650
R8 = 715
and the impedance of the average line.
k
MBA568
time
and an average line
(120 nF // 1100 ), the
Product specification
TEA1065