Rusted Morsematics

On the Subject of Rusted Morsematics

Lost in the garbage dump of dead modules, it thought it’d never see the light of day again...

Attention Expert! We have found this disarmed module abandoned by the Bomb Defusal Corp... but it seems to still be active! Whilst looking through the old records, we have recovered this manual excerpt:

Interpret the signal from the flashing light using the Morse Code chart.
The signal will play once upon pressing “PLAY”.
The signal will be a maths question, encoded in the format <a> <op> <b>.
A response to the signal is entered using the dot, dash, and space buttons. The answer is submitted by pressing “OK”.
Your response is shown in the display. If you make a mistake, press “NO” to clear it.
Warning: “NO” can only be pressed when the correct answer has a matching number in the time remaining, or when less than 30 seconds remain.

However, we believe the wiring is slightly malfunctioned, and the module acts differently to its original state.

Firstly, the flashing Morse Code signal doesn’t match any numbers for the maths question. They seemed to have been modified by taking the first two serial number characters as Base-36 digits and converting them into 5 digit binary.
Then, the a variable’s digits swap from a dot to a dash or vice versa in the same position where there is a 1 in the first serial digit’s binary sequence, and stay unchanged where there is a 0.
Likewise, the b variable’s digits are modified based on the second serial digit’s binary sequence in the same way.
Note that if any of the Base-36 digits are higher than 31, use 31.
Also, the operator’s signal now plays each letter in reverse. It looks like it only can show the operators “ADD”, “SUB” and “MULT”.
The “PLAY” button works as many times as needed, and can be stopped at any time by pressing “PLAY” again.
Furthermore, the “NO” button can be pressed freely, it seems the module thinks there’s always less than 30 seconds left. Silly module.