SIGMA BENEFON TDP-52-SN3 - Manual (Page 46)

27.1.1999
4A0701GB.__1 12
Product: TDP-52-SN3 (Sigma Gold) / OA0700 Audio
detection level standard. Once the detector judges a valid FFSK signal, ’H’
signal is put out on the FFSKDET pin (pin43). The data detector speed is
determined by the external condensator C438.
FFSK DEMOD. To recover 1200bps receive data and clock from the FFSK
signal fed on DEM1 pin.
The modem is connected to the CPU by series lines, the receiver to a
synchronised gate, and transmission is directed to an ASIC series output. The
modem provides a 1200 Hz clock signal RXCLK to the processor and TXCLK
to ASIC.
5.1.10 The DTMF Generator/Receiver
The DTMF generator provides all sixteen standard DTMF tones, and each
individual frequency separately. The generator is used to produce both key and
alarm tones and enable numeric message transmission during a call.
Key and alarm tones are taken from the generator to switch DTMFRXON and
is summed with the rx-audio signal. Key tones are connected to earphone and
external earphones.
When transmitting a numeric message, the DTMF tones produced by the
generator are fed through the VR8, which set the DTMF signal level to the
switch DTMFTXON, and then the signal is summed with the tx-audio signal.
The DTMF receiver takes in numeric messages sent to the phone. The route to
the DTMF receiver splits from the rx-audio signal after the summing junction
ADD4.
5.1.11 Signal level detectors
Audio signal level detectors are required for the HF-function to measure the
transmitted and received audio signal level, and to study the data signal level.
Measurement is done by rectifying the signal, and the resultant DC voltage is
read by a phone’s prosessor A/D converter. TXDET is at the transmission side
detector and RXDET is at the receiver side detector.
5.1.12 Compander/Expander
Compander and expander units are included in audio asic I405 and can be
controlled by registers.
5.1.13 Alarm buzzer
Tones for the internal alarm tones are provided by the DTMF generator. The
internal alarm tones path way is DTMF generator, VR8, switch DTMFRXON,
summing junction ADD4, VR11, AMP5 and buzzer. The buzzer volume is
controlled by the DA3.