Item box

Item Boxes, or Monitors, are destructible containers that contain various power-ups or bonuses that can be collected by Sonic or other player characters. In their early appearances, they appeared as small television sets, with the screen depicting an icon of the power-up contained inside. (Sometimes these sets could also display static.)

Since Sonic Adventure, they had a redesign to look more like glass capsules with the icon picture inside. These item boxes could be activated by simply touching them while monitors needed to be attacked.

Monitors sometimes make returns, such as in Sonic Heroes, Shadow the Hedgehog, Sonic Unleashed and Sonic 4

There is also one alternative form of monitors. Those are balloons. These balloons are red and they have a blue circle with a star on them. They act like capsules, except that they are always in air. They first appeared in Sonic Adventure 2, continued on Sonic Heroes and been used only in spin-offs such as Mario & Sonic at the Olympic Winter Games since.

While some of these items are protective against hazards, spikes and enemies, they cannot protect you from instant death such as being crushed or falling below the zone.

Classic Power Ups
There have been other different types of Power Ups throughout the series, some specifically to certain games, but listed above are the usual Power Up found in all games.

Monitors never used
Goggles Considered to have same effect as later Liquid Barriers only were never used in Sonic 1.

Eggman and the S monitors would have appeared in Sonic 1, though they did not, their graphics are still in the game. The S monitor served a similiar role in the early Sonic CD prototypes, but only allowed the player invincibility and speed increase.