Relay

An electromagnet and a set of contacts. A small current in the magnet's line switches a different line. This is how a weak signal (a Coherer, a Breaker a Controller switches) works something that draws a lot.

Crafting

W P W
C C C

W is Copper Wire, P is an Iron Plate and C is Ceramic.

Using it

Put the relay directly against an Electromagnet (any side). Wire the magnet into one line and the relay into another. The relay is a wire in the second line: open until the magnet's field is strong enough, then closed. It does not join the magnet's line, even though they touch.

• Pulls in when the magnet's field reaches 60%, lets go below 30%. The gap stops a weak coil from chattering.
• To let a Controller switch a big load: put a Breaker in the magnet's line and give the controller a Switch card for it. To let a controller watch the big load, link a Current Sensor on the relay's line.

It wears when it switches under load

Like a breaker, opening with current flowing draws an arc that pits the contacts (1% per amp broken), and the arc is a spark other detectors can hear. Carrying more than 4 A wears it a little each tick. Closing, holding and sitting idle cost nothing.

Worn contacts let go late: each tick it should open, it manages it with a chance equal to its condition. It never refuses. Its condition bottoms out at 20%.