The RAE 4/30 series was a further development of the RAE 4/15 first-generation transistorised architecture.
The mechanical design remains essentially the same with cosmetic changes to the case and keyboard layout. The main functional changes from the 4/15 concern the number of storage registers.
Operation follows modern arithmetic conventions, unusual for a first generation machine. That is, there are no += and -= keys, operations are entered arithmetically:
Negative numbers are displayed conventionally with the minus lamp illuminated and are handled correctly according to arithmetic rules. Negative numbers are entered by pressing the "-" key before the first digit of the number.
Products greater than 15 digits are handled by displaying the high order digits directly, pressing the ^ key displays the lower order 15 digits.
The right-arrow key provides decimal shift and roundoff control. Each press reduces the resolution by one decimal place and rounds the least significant remaining digit according to the value of the digit that was discarded.
Two memory registers are provided, with keys to add,subtract, display and clear each register.
Power-on reset is not guaranteed, the clear keys must be specifically pressed after power-on.