I had a very bad initial thought....
but not good for YA, I suspect.
You bad girl, you. I'm beginning to think the nun issue wasn't an accident after all.
A couple of suggestions Alc:
An EM pulse - might need a lot of power for that one but maybe not for short range and I don't know what else it could be used for. Also it might take out a lot more devices than just the target!
A strong static discharge - the bain of electronics. Again not sure what it would be used for otherwise.
Maybe some sort of tazer device might do it. Though I don't know if they work without actually firing darts into the target and that might be a problem for an electronic device if you don't want it physically damaged. possibly a simple modification could be done to the tazer so it doesn't fire any darts but still discharges. Held close to the device that might be enough to do it. Probably wouldn't work on a military device hardened against such things.
It'll be civilian spec and reasonably experimental. I'd thought of tazer too, but I can't think of a way to wangle that into the story yet.
Implanted? the only way to access it will be electro-magnetic pulse, and quite a powerful one. Nobody's going to quibble if their telephone fries when he's struck by lightning, but they will if thousands burn out every time there's a thunderstorm. Directive would be wise; putting out that much power in omni would tend to get you noticed (if it's strong enough to burn out one, it would jam thousands.) This is starting to sound like maser technology, single high amplitude narrow pulse tuned to telephone frequency, burning out the RF and probably the IF stages, preferably (since you mention the guy is a friend) without overheating too much surrounding tissue (which might or might not be brain tissue. Sure, the transducers will be in the head, but it might be more efficient to have a wire, and put the receiver/transmitter circuitry somewhere else). That's not going to be widely available parts, unless you can retune the generator of a microwave oven (away from the standard water frequency, we don't want to bring the guy to the boil) and find exactly the right frequency molecule for the gas tube/crystal.
The implant is currently in the mastoid process, the bony bit behind the ear. It can be moved though. I'm imagining it having an access point under the skin, much like the ports chemotherapy patients have implanted in their abdomens for the drugs to be injected into. I imagined the access point would be used for diagnostics or updating software. Slice the skin, and you have access. Now having thought about it, I might be able to disable it with a (computer) virus. I'm not sure how smart this implant would be -- maybe the processing would be done remotely, but it may still be a runner.
Maser is an option, ty. I've been looking it since you suggested it, but I'm not sure of how to wangle that in either.
Not sure if I'm adding or helping much, but how about a mobile phone in appearance? Almost everybody has one.
As to what could do the job - if you could explain away how you'd get the power necessary in a small device, how about a taser (they make some of them that look like a mobile, very illegal in most countries) that fires darts, the wires transmitting an EM pulse?
Alternatively, but again needing massive amounts of power (MW levels, I believe), you could look at something like electronic countermeasures used for jamming radar and communications. The problem would be to get it in a small enough package and, considering what some systems are capable of, keeping the settings low enough to only jam or permanently disable the implant without hurting the person. And again, you could end up jamming everything in the vicinity without tight focus.
Yup, that's where the maser reading took me, countermeasures. May be an option.
Do you need it to look like an everyday object, Alc, or does it not matter?
To give some context, my heroes left Earth in 2090, so technology has moved on. The scene is in a garage, but one that has a part in many engineering projects, so I can use almost any device. Using a military device would be a problem, however, since the characters shouldn't have access to it. So, ideally, I'm looking for a tool (settle down, springs, settle down).
Thanks for all the replies everybody. It's generating ideas.
