TEA1068T Philips Semiconductors, TEA1068T Datasheet - Page 7

• Manufacturer Part Number: TEA1068T
• Description: Versatile telephone transmission circuit with dialler interface
• Manufacturer: Philips Semiconductors

Philips Semiconductors
If fixed values are chosen for R1, R2, R3 and R9, then
condition (1) will always be fulfilled, provided that
suppression, condition (2) has to be fulfilled, resulting in:
Z
k
Scale factor k (dependent on the value of R8) must be
chosen to meet the following criteria:
1. Compatibility with a standard capacitor from the E6 or
2.
3.
In practice, Z
cable type; consequently, an average value has to be
1996 Apr 23
handbook, full pagewidth
R8//Z
bal
Versatile telephone transmission circuit
with dialler interface
(R8/R1).
E12 range for Z
ensuring correct anti-side-tone bridge operation
gain.
Z
Z
(R8/R1) Z
bal
bal
bal
//R8 << R3 to fulfil condition (1) and thus
+ R8 >> R9 to avoid influencing the transmitter
<< R3. To obtain optimum side-tone
line
line
varies greatly with the line length and
bal
k
Z
line
Fig.5 Equivalent circuit of TEA1060 family anti-side-tone bridge.
, where k is a scale factor:
Z line
V EE
R1
R9
SLPE
LN
i m
R8
7
R2
chosen for Z
long lines.
Example: the balanced line impedance (Z
optimum suppression is preset can be calculated by:
Assume Z
5 km line of 0.5 mm diameter, copper, twisted-pair cable
matched to 600
then R8 = 390 ; Z
The anti-side-tone network for the TEA1060 family shown
in Fig.5 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.
Figure 6 shows a conventional Wheatstone bridge
anti-side-tone circuit that can be used as an alternative.
Both bridge types can be used with either resistive or
complex set impedances.
R3
Z bal
IR
line
bal
= 210
, thus giving an optimum setting for short or
(176 /km; 38 nF/km). When k = 0.64,
R t
bal
+ (1265 /140 nF), representing a
= 130
MSA500
+ (820 //220 nF).
Product specification
TEA1068
bal
) at which the