They have the ability to communicate with each other telepathically through radio waves. The people of the One Piece world take advantage of this ability by attaching buttons and receivers to them.
Types of Transponder SnailsEdit
The Transponder Snail appear in many varieties, depending on who owns them and who is talking. They are sometimes designed to resemble their user. Marine Transponder Snails typically have the Marine symbol painted on their face or on their shell. Despite their varied appearances, there appear to be general categories by which Transponder Snails are classified.
Regular Transponder SnailEdit
The most common type of Transponder Snail commonly seen. They are too big to be conveniently carried around, but their signal range is much further than that of a baby. They can also serve as fax machines if the right accessory is attached. They are capable of making long distance calls, and many are large enough to make a worldwide signal. The Marines are shown to often favour these over Babies in field communications due to the range, carrying them around with the help of a shoulder strap.
Baby Transponder SnailEdit
A Baby Transponder Snail is a fairly small and portable Den Den Mushi, enough to fit in one's palm. It's good for keeping in contact with fellow comrades in the same area, but incapable of inter-island calls. They can also be used as speakers, in which to broadcast the user's voice throughout the area.
Black Transponder SnailEdit
The Black Transponder Snail is a type of Transponder Snail used commonly by the Marines, as listening devices or "wiretaps", to intercept calls between pirates or other miscreants. They are actually a different type of species compared to other types of Transponder Snail. They do not grow as they age and remain a small portable size for the rest of their lives. They enjoy eavesdropping, and dislike communicating with others. Their abilities to intercept can be blocked by their counterpart, the White Transponder Snail.
Golden Transponder SnailEdit
The Golden Transponder Snail is a special kind of Transponder Snail which is only held by the Marine Admirals. It is used to summon the Buster Call attack. The Den Den Mushi is immobile and its entire body appears to be made out of gold.
It is a very rare type of Transponder Snail. After the button on its back is pressed, it sends a message straight to the Silver Transponder Snail, which is the signal for the Marines to start the Buster Call.
So far in the series, it has only been shown to be used twice: once by Spandine on the Island of Ohara, and again, twenty years later, by Spandam with false permission from Admiral Aokiji. While Spandine's use of it was intentional, Spandam's was not; he used the Golden Transponder Snail by accident because he thought it was a Transponder Snail, which he was also carrying, and wrongfully pulled out the Golden Transponder Snail and activated it without looking to see which Transponder Snail of the two he had actually grabbed.
Silver Transponder SnailEdit
The Silver Transponder Snail is a special type of Transponder Snail, used as an alarm to alert the Marines through the Golden Transponder Snail's Buster Call request. It is depicted as an elderly snail that is bearded and old-looking. It has a shell that appears to be made of solid silver and similar in design to the Golden Transponder Snail. Unlike regular Transponder Snail, when this one receives a Buster Call signal from a Golden Transponder Snail, it gives off a loud vibrating sound that alerts any and every Marine nearby.
Surveillance Transponder SnailEdit
The Surveillance Transponder Snail is a type of Transponder Snail that acts as a video camera. They come in two sizes. The small Surveillance Transponder Snail are mounted in specific locations around a building with an antenna connected to the shell. They are all connected to a larger Surveillance Transponder Snail that is able to pick up the signals. These large ones are connected to a machine which produces video feeds to a set of monitors. In the event that the smaller one spots an intruder, it will send a signal to the larger one, which will cause its red eyes to begin flashing in an alternating manner, and make a buzzing noise to alert the security guards watching the monitors.
Visual Transponder SnailEdit
The Visual Transponder Snail is similar to the Surveillance Den Den Mushi, and it broadcasts what the Transponder Snail sees to a bigger video screen. The smaller Transponder Snail (which seems to be larger than the Surveillance variation) are used as the cameras, while the larger ones are linked to the screens to receive the signals. These visual versions seem to be able to broadcast their frequencies between two relatively close islands.
White Transponder SnailEdit
The White Transponder Snail can be attached to other Transponder Snail. They send out psychic waves that prevent calls from being intercepted; in a way, they are the opposite of the black Transponder Snail. They are rare and one was first seen used by Monkey D. Dragon to communicate with Emporio Ivankov.