A modular diagnostic ultrasound apparatus is provided comprising a core unit, system electronics and an I/O port. The core unit comprises a housing and a system electronics package within the housing. The system electronics has one or more concatenated filters, including a front end transmit/receive circuit, a processor, a back end circuit for scan conversion, a system clock and a programmable system memory device. There is at least one I/O port connected to the front end and the back end of the system electronics package and extending through the core unit housing wherein all system data processing information is transmitted or received through the I/O port.