Most technomages focus on quads — QUick And Dirty Devisements. Using a standard quad kit, they can gin up a circuit in 10-20 minutes. These have several limitations, including low battery life and fragility (it’s easy to knock breadboarded wires loose).
Quads are not intended to be permanent, they are temporary creations for use in exigent circumstances. That said, well-done wiring, a sturdy circuit board, and quality soldering can make a quad as resilient as most electronic devices.
Some devisements, on the other hand, are more-or-less permanent. These are invariably built using “slow and steady” methods.
These require weeks or months of work by a dedicated technomage (as only one craftsmen can work on one devisement), frequently with hazardous substances. (And chemists laugh.) The benefit being that they are far more rugged and reliable, and can be powered with ambient current.
All technomage devisements are built around electrical circuits, and all require a power source of some kind. In most cases, this power source is a fundamental component of the devisement, meaning only a technomage can change the battery. (The first technomagical devisements required it be the same technomage who crafted it, but advances in crafting methods sidestepped that restriction.)
This is obviously quite limiting, especially for items which are meant to be used by non-technomages. Quite recently, technomages developed a way of powering devisements with the ambient energies of a person’s body. (These methods are used in crafting, e.g., shadowjacks and steed collars.)
This method requires two very esoteric substances — firegold and frostsilver — which require special tools to create and work, and which are inherently hazardous. Most “slow and steady” creation methods require a large and well-equipped craft room, which is why the typically nomadic Guns tend to favor quads.