MCSO Code 20

Every night when I listen in, I hear the dispatcher do a Code 20, and the officers report back with a code. Is this some sort of Welfare check on their officers, using 2 Factor Authentication codes based on the time of the code 20 ?

DPS and MCSO use Code 20 as a welfare check. Peoria uses Code 900. I'm not familiar with other agencies enough to know what they use.
MCSO generally does it as a roll call, and each deputy responds with their badge number.
DPS generally does it when a trooper has been on a traffic stop for a specific length of time without radio contact with their dispatcher.
Peoria does it when an officer has been on a traffic stop or any other call for a specific length of time without radio contact with the dispatcher.

John
Peoria

the LRV's (light rail metro) drivers do a back n forth welfare check too- they have to respond with a "Code 4" for an OK sign. I believe it is done every 15 mins I could be wrong.