What is the digital mode available on the DR-135/235/435T and DJ-596T ?
The EJ-40U/EJ-43U optional digital boards consist of a CVSD (Continuous Code Delta Codec), a CPU and GMSK-MODEM (Gaussian Minimum Shift Keying-Modem circuits. The analog voice signal from a transmitter’s microphone is encoded by CVSD to a 14kbps digital signal while transmitting (Analog-Digital conversion). This digital signal is processed in the CPU using the publicly-open ITU-TV.32 protocol. This processed signal modulates the VCO in GMSK direct frequency modulation using a GMSK-Modem. It is then transmitted as a 20F3E conventional FM signal. In the receiving mode, the GMSK modulated RX-AF signal comes out of a demodulation circuit and is processed at the GMSK-Modem. This signal is again processed in the CPU, then decoded in CVSD to obtain the original analog voice signal (Digital-Analog conversion). As in a normal FM receiver, the signal is amplified for output to a speaker. Definitions: CVSD: Continuous Code Delta Codec. One of the delta modulations that is commonly used for A-D,D-
