The Model 405 SGLS Modem comprises a configured set of modulation and demodulation functions housed in a 5.25-inch rack-mounted Modular Subcarrier Subsystem chassis. A functional block diagram of the Model 405 is shown below.

The Modulator section of the unit consists of the SUM005 Signal Summer and the PMM004 Phase Modulator. Optional PSK subcarrier modulation (B/Q/U/A PSK) and FSK003 AM/FSK (SGLS) Modulator functions are also available.

The Optional Demodulator section consists of the RDM021 IF Receiver/Demodulator, which includes a Linear Phase Demodulator and PSK Demodulator with dual Bit Synchronizer(s). The demodulation functions are firmware configured to meet specific customer needs. SGLS AM/ FSK demodulation for Echo Check is also available as an option.

The CPU010 Control Processor provides control of the unit via either the local front panel VF Display and keypad or the Remote Control Interface.