I need to make an item (probably a bell) that when rung will ring an identical bell in another regio. Someone in our group thought they remembered seeing an item like that in an Ars book but we can't remember which one.
The best way for me to do it would be by using Rego Terram and then have the bells be arcane connections to one another. Was thinking I could use the base level of 3 for controlling dirt in an slightly unnatural way as a starting point but am interested in getting some other thoughts on the matter.
It's not exactly what you are asking, but maybe it answers the same problem. If I understand correctly, you want to make it so that when you ring the bell at location A, the bell at location B will also ring. Why then not get an Arcane connection to location B, and cast on the bell at location A the following:
The Voice of the Distant Bell
Rego Imaginem Level 30
R:Touch, D:Ring, T:Ind
You trace a ring on the outer rim of a circular bell (ideally, the ring has already been engraved there). As long as the ring is not physically broken, the sound of the bell does not seem to come out of the bell itself, but from any distant point of your choosing, to which you must have an Arcane Connection when casting the spell.
Base 15 "Make an object appear (to one sense) to be in a location to which the caster has an Arcane connection", +1 Touch, +2 Ring
Note that the bell has no sound at location A, and only the sound at location B, but it seems quite close to what you are looking for. Also note that this is a single, non-ritual spell. Thus, if you can spont it (or have someone spont it for you), or have a casting tablet for it, you need not spend any time or vis to have an effectively "permanent" effect. And if you are forced to learn it, than you can sell "magical bells" to the whole Order for a pawn a dozen.
Alternatively, if you want to make a lesser enchanted item with Rego Terram, you can enchant a magical item with the following effect:
Rego Terram Level 39
R: Arc, D: Sun, T: Group
Synchronizes a group of up to 10 bells (an Arcane Connection is needed to each) so that when one rings, all the others do.
Base 1 "Control or move dirt in a natural fashion" (note that ringing a bell is natural) +2 metal, +4 Arc, +2 Sun, +2 Group
with 4 levels added for 2 uses/day and an environmental trigger
But if you are going the enchanted item way, it's probably better to enchant a bell with the following effect (triggered by shaking):
Creo Imaginem Level 15 (or 20)
R:Arc D:Mom T:Ind
Creates the sound (and for an extra magnitude, the image) of a bell at a distant location (an Arcane connection is needed).
Base 1 (or 2), +4 Arc, with 10 extra levels for unlimited uses
You can bump it down a magnitude if you think 24 uses/day are enough, depending on what you need the bell for. So a bell that only projects sound (no image!) at a distant location up to 24 times/day can be created as Level 10 Lesser enchanted item costing a single pawn of vis and a season of work. This is easily within reach of an apprentice.