H.E. furnace Humidifier ?

Inspected 2 HE furnaces that had humidifiers but not the typical duct from a pad going to the supply plenum. It had a thermostat wired to a small black box with water supply. I have never seen this type of humidifier - being so small, is there even a pad in this square unit.
Can someone identify the type of humidifier and and inform me how this type works or direct me to info on line about it.
Thank you for the help.

After searching the internet, I found what type this is - It’s a mist humidifier.
Never saw one , I have copied from their manual the below info for those who are interested in learning this type.
MISTER brand -
Your atomizing mister type humidifier operates by dispersing a fine mist into the warm air plenum of your furnace. The
water is then evaporated and carried into the home by the furnace air flow. This humidifier is recommended for areas
where water mineral content is low. When wired properly, the humidifier will operate only when the plenum temperature rises to
the internal thermostat setting, the humidistat senses a need for humidity, and the furnace blower is in operation. The
internal thermostat controls the temperature at which the humidifier will turn on. The humidifier should activate after the
furnace blower comes on and shut off before the furnace blower turns off.

I agree. Mist type.

The problem is keeping them working and that is dependant on water quality and regular maintenance.

Yes the manual states hard mineral water can cause havoc - my wording of course.

Keeping one maintained and serviced is the key AND why …

SoP exclude them in the major associations