Phosphor Screen

A sealed glass envelope coated inside with glowstone dust, which glows where a signal lands. Pair it with an Oscilloscope.

Crafting

A Glass and two Glowstone Dust, in any order.

Sealing it

Set it on a Firebox and let it heat. Right-click with an empty hand to pinch the envelope off. The gas sealed inside contracts as it cools, which makes a partial vacuum: the hotter you seal it, the better the vacuum. A Pressure Gauge reads it (negative is vacuum). It glows only when it is sealed and the gauge reads below about -0.3 Pu.

Using it

Put an Oscilloscope against it. The screen has four brightness levels and gives light to match.

Overrun

• Reheating a sealed envelope past the heat it was sealed at turns the vacuum into pressure. Above a small pressure it may shatter, certainly if pushed far, and past the glass's service temperature it cracks outright. Nothing is returned.
• Burn-in: a screen held at full brightness slowly burns, and each third of burn costs the brightest level it can show, for good. Do not leave a maxed signal on it.