As shown in Fig. 3.1, the 224X is divided into 11 major functional modules: 1 Control Head 2 Transition 3 Single-Board Computer (SBC) 4 Nonvolatile Storage (NVS) 5 Timing and Control (T&C) 6 Data Memory (DMEM) 7 Arithmetic Unit (ARU) 8 Floating Point Converter (FPC) 9 Audio Input (AIN) 10 Audio Output (AOUT) 11 Power Supplies (PS1 , PS2, and PS3) for the control head, Transition module, and power supplies, all modules plug into an 8-slot card cage and are interconnected via a motherboard. The card cage and the power supply are contained in a mainframe. The control head is connected to the mainframe by a 25-conductor cable. The Timing and Control (T&C), Data Memory (DMEM), and' Arithmetic Unit (ARU) modules comprise a dedicated, 293-ns-cycle, microprogrammed digital signal processor (DSP). During normal operation, signal flow begins with the two audio input channels. The Audio Input (AIN) module filters, samples, and digitizes analog audio signals into .14-bit floating point representations (12-bit mantissa, 2-bit exponent). These floating point representations are then converted into 16-bit fixed-point two’s complement numbers by the Floating Point Converter (FPC) module. The DSP processes this information and generates up to four.independent channels of output data. This processed data is passed back to the FPC module, which reconverts it into floating point form. To generate the audio output, the Audio Output (AOUT) module reconstitutes four analog signals from the digital data stream. The Single Board Computer (SBC) module is a controller that interfaces the control head to the DSP. The microprocessor (an 8080) on the SBC module scans the switches and pots on the control head and drives the control head displays. It processes the information- received from the control head and changes the program running in the DSP. In addition, the SBC module performs various housekeeping tasks, such as power-up diagnostics and storing and retrieving nonvolatile user setups from the Nonvolatile Storage (NVS) module.