Add "How it works" section to readme

README.md

@@ -1,9 +1,20 @@
 Alternative Firmware for BTT Relay v1.2
 
 ATTENTION!
-The relay board contains high voltage area, which may reault in serious harm to the operator (even death).
+The relay board contains high voltage area, which may result in serious harm to the operator (even death).
 The author assumes no liability which may come from using the software or by following the instructions included in this project.
 
+How it works:
+1) AC power on to relay
+2) relay powers the printer main power supply.
+3) after 60 seconds the relay looks for PS_ON signal to be high (over 1 Volt).
+4) if PS_ON if high, then relay goes to "running" state and awaits PS_ON to go low (0 Volts).
+5) if PS_ON is low, then the relay will go to "power delay" state, which means it will shut down after 20 seconds.
+6) when the relay shuts down (cuts power to the printer) it will go into "recovery delay" state for 30 seconds.
+7) after recovery delay, the relay will go into "tripped" state, where it will reset itself if PS_ON signal goes to high.
+At any time, if enabled, the short-circuit protection can be engaged, when 5V_IN signal is lower than 4.5 Volts.
+The relay can be reset at any time, from eny state, by shorting the reset pin on board to relay 5V pin (momentary switch). If these 2 pins are always shorted, then the relay is disabled, thus providing power to the printer with no control over it. Relay states are signaled via on-board leds.
+
 It is using platform.io and written using C language.
 All the build requirements should be automatically handled by platform.io.
 Development environment assumes you are using vscode with platform.io installed and have a 5V serial adapter to flash the MCU.