Welcome to the forum.
Those circled "buttons" are actually over-current protection circuit breakers.
Those breakers are shown in the normal condition. If either should sustain an over current condition, then the center post would pop out, usually exposing a red band. When in that state no voltage / current is available to the circuit.
When the circuit breaker has tripped, w/ the center post extended, then power restoration is possible by pushing and latching the center post back to the normal condition shown in the image.
The key switch has three positions: OFF / ON / DISCHARGE.
Normal head usage requires the switch in the ON position.
Macerator overboard discharge requires the seacock be placed in the open position and the key switch (probably manually held) in the DISCHARGE position.
Note the boat must first be the required distance off shore before discharging waste. The seacock must otherwise be locked closed. On my boat I close and remove the seacock handle, which is an acceptable method for locking it closed.
