PSB21384HV1.3 Infineon Technologies, PSB21384HV1.3 Datasheet - Page 144

• Manufacturer Part Number: PSB21384HV1.3
• Description: Telecom ICs AMuLaw/Speech CODEC w/ ST Transceiver
• Manufacturer: Infineon Technologies

Specifications of PSB21384HV1.3

• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

Data Sheet
4.4
The speakerphone option of the SCOUT-SX performs all functions required for echo
suppression without any external components, just by software. All these operational
functions realized by the signal processor are completely parameterized. This technique
offers a high level of flexibility and reproducibility.
Basically, three static mode of operation can be distinguished: “transmit mode”, “receive
mode”, and “idle mode”. In the speech mode the receive path is attenuated while in listen
mode the attenuation is switched to the transmit path. In the idle mode the attenuation is
halved between transmit and receive paths. The amount of switchable attenuation can
be chosen by software. The speakerphone goes into transmit mode if both, the speech
detector and the speech comparator SCAE, indicate the presence of a speech signal in
the transmit direction that is strong enough. Switching into receive mode appears if the
speech comparator SCLE and the speech detector in the receive path both detect a
speech signal that is strong enough. If no speech is detected at all, the speakerphone
goes into idle mode.
As the signal flow graph of the speakerphone option shows (see figure Chapter 78), the
complete operational algorithm is situated between the analog front end/signal
processing and the compression/expansion logic. Thus telephone sets can be optimized
and adjusted to the particular physical and acoustic environment.
The main features of the speakerphone signal processing are:
• Two separate attenuation stages activated by voice, one for the transmit and one for
• Immediate mode switching mainly controlled by two comparators, one at the acoustic
• All parameters can be adjusted independently and are closely related to the physical
• Speech detection by special speech detectors in the respective transmit and receive
• Background noise monitoring to eliminate continuous background noise from speech
the receive path. They are controlled by the current and past speech activities.
side and one at the line side. Capable of handling very long echo times.
phenomenons.
directions. Different time constants are separately programmable for signal and noise.
control. All time constants are user programmable.
Speakerphone Support
134
PSB 21381/2
PSB 21383/4
2001-03-12
Codec