Throughout the Three Investigators series, Jupiter Jones was a whiz not only at solving the mysteries but at coming up with some neat equipment and ideas along the way. This section is intended to describe a few of the more notable inventions that he developed. If you think of other memorable inventions, let me know.
The business card - One of the first things that we as readers discover about Jupe is his desire for publicity for the Three Investigators. To that end, Jupe develops business cards that the boys can hand out. We've seen a rendering of that card in every book, but we still like the simplicity of it. The card read as follows:
THE THREE INVESTIGATORS
The question mark symbol - Jupiter decided early on that the question mark would be the trademark of the Three Investigators because "they stand for questions unanswered, riddles unsolved, mysteries unexplained," (or similar verbiage). The boys used the question mark on their cards to attract attention, but they also used the question mark to mark their trail and to mark important locations.
The colored chalk - After Bob and Pete's visit to Terror Castle while Jupiter is laid up with an injured foot, Jupiter develops the use of colored chalk to mark trails and objects. The boys have three colors of chalk: white for Jupe, blue for Pete, and green for Bob. The chalk is used quite a bit in the Robert Arthur stories with less use in the stories written after his death. Jupe and Pete mark their path in the final assault on Terror Castle, Pete and Hamid mark the warehouse door where they escape from the mummy case in "Whispering Mummy," Bob and Pete mark their trail in the mines of Verdant Valley in "Green Ghost," and the list goes on.
The Ghost to Ghost hookup - Developed by Jupe in "Stuttering Parrot," the Ghost to Ghost hookup was designed to get a lot of kids looking for something or someone at once without each person having to be personally contacted by the Three Investigators. Jupe, Pete, and Bob would each phone five friends and ask for the requested information. If none of those fifteen boys could help, then they would pass the message along to five each of their friends. The sheer numbers involved made it possible to mobilize the kids of Rocky Beach in a short time to be on the lookout for whatever person or object the boys were hunting. Jupe named it "Ghost to Ghost" because they would most likely not know who would be calling with information, and the voices on the phone would appear like "ghosts" to the boys, plus the name has flavor and color. The down side to the hookup was that all the phones in Rocky Beach would have busy signals while the messages were being passed along. The Ghost to Ghost Hookup helps out in several cases, including "Stuttering Parrot," "Whispering Mummy," "Crooked Cat," "Shrinking House," and others.
The directional signals - First described in "Crooked Cat," the directional signals were three boxes with electronic circuitry and antennas, each of which could be used to track the location of the other two boxes. This allowed the boys to locate each other when it wasn't practical or possible to use the walkie talkies. In addition, each box had a microphone and associated circuitry so that when the word "Help" was spoken near one unit, red lights on the other two units would blink, thus alerting the Investigators that one of them was in trouble.
The See-All - With Headquarters being hidden by junk, it was not possible for the boys to see out directly into the Salvage Yard. Therefore, Jupiter invented the See-All, a periscope of sorts constructed with stove pipe and mirrors that went through the roof of Headquarters and allowed the boys to see what was happening in the area outside Headquarters. This invention was described first in "Whispering Mummy" and used in several subsequent cases.
Walkie-talkies - Although common these days, walkie talkies were a rarity in the 1960s when the Three Investigators books were first written, and Robert Arthur made sure that the boys were outfitted with them. Jupiter built a set of three units that used a wire sewn into a belt worn around the waist for an antenna. The units could both send and receive but had a limited range. They were first used prominently in "Whispering Mummy," when first Pete and later Jupe were trapped in the mummy case. Bob also used the walkie talkie in "Vanishing Treasure" to discover Rawley's destination at the harbor so that Jupe and Pete could be rescued.
The speakerphone radio - With three boys in the detective firm and only one phone in Headquarters , it would be difficult for all three to talk on the phone at once. Therefore, Jupiter took parts from an old radio and built a speakerphone, whereby all three boys could hear what was going on, especially when Alfred Hitchcock called and wanted them for a case. First used in "Terror Castle."