Advertisement
Each subframe consists of the following four fields:
- A 2-bit Preamble field
- An 8-bit Data Channel field
- An 16-bit Sync Word
- A 72-bit ADPCM Payload (CRC 8-bit)
9.3. Signal Flowchart in the Whole System
Reception
CN1 of the base unit is connected to the TEL line, and the signal is input through the bridge
diode D4. While talking the relay (Q4) is turned ON and amplified at the amplifiers Q50, then led
to DSP (IC201). DSP generates ADPCM signal. The ADPCM signal is input to RFIC (IC101) of RF
UNIT. RFIC outputs FSK modulated RF signal. The RF signal is passed through filter (L111) to
be transmitted from the antenna. As for the handset, RF signal from the antenna is input to
RFIC passing through filter (L111) then input to DSP (IC201). DSP performs ADPCM decoding to
convert the signal into the voice signal, then it is output to the speaker.
Transmission
The voice signal input from the microphone is led to DSP (IC201). The DSP generates ADPCM
signal. As well as the reception, it is converted into the RF signal by RFIC (IC101). Passing
through filter (L111), it is transmitted from the antenna. As for the base unit, RF signal from the
antenna is input to RFIC (IC101) passing through filter (L111) and the balum then input to DSP
(IC201). DSP performs ADPCM decoding to convert the signal into the voice signal. The voice
signal is amplified at the TX amplifier (Q1), then output to the TEL line (CN1) through the relay
(Q4) and bridge (D4).
Advertisement
