TEA1069AH View Datasheet(PDF) - Philips Electronics
Part Name
Description
Manufacturer
TEA1069AH Datasheet PDF : 44 Pages
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Philips Semiconductors
Versatile speech/dialler/ringer with
music-on-hold
Product specification
TEA1069; TEA1069A
SIDETONE SUPPRESSION
Suppression of the transmitted signal in the earpiece is
obtained by the anti-sidetone network comprising R1//Zline,
R2, R3, R8, R9 and Zbal (see Fig.10). The maximum
compensation is obtained when the following conditions
are fulfilled:
R9 × R2 = R1 × (R3 + R8)
(1)
k = R3 × --((--RR-----82-----+×-----RR----99----))-
(2)
Zbal = k × Zline
(3)
The scale factor k is chosen to meet the compatibility with
a standard capacitor from the E6 or E12 series for Zline.
In practice, Zline varies considerably with the line type and
length. Therefore, the value chosen for Zbal should be for
an average line length thus giving optimum setting for
short or long lines.
Example: the balance impedance Zbal at which the
optimum suppression is present can be calculated as
follows:
suppose Zline = 210 Ω + (1265 Ω//140 nF) representing a
5 km line of 0.5 mm diameter, copper, twisted-pair cable
matched to 600 Ω (176 Ω/km; 38 nF/km).
When k = 0.64 then R8 = 390 Ω;
Zbal = 130 Ω + (820 Ω//220 nF).
The anti-sidetone network for the TEA1069 and
TEA1069A shown in Fig.10 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 11 shows a conventional
Wheatstone bridge anti-sidetone circuit that can be used
as an alternative. Both bridge types can be used with
either resistive or complex set impedances. More
information on the balancing of anti-sidetone bridges can
be found in our publication “Applications Handbook for
Wired telecom systems, IC03b”, order number
9397 750 00811.
handbook, full pagewidth
LN
R1
Zline
VEE
R9
R2
im
IR
Rt
R3
R8
Zbal
SLPE
MSA500 - 1
Fig.10 Equivalent circuit of TEA1069 and TEA1069A anti-sidetone bridge.
1998 Jan 08
13
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