A 7b9 — E9 Pedal Steel
A 7b9 has no bar or slant position on the E9 Pedal Steel with the pedals up.
A 7b9 stacks A – Bb – C# – E – G, and with every pedal up and every lever at rest no bar position on the E9 Pedal Steel sounds that set: at every fret, and on every short slant, a tone it needs is missing or too few strings carry it.
A pedal steel does not stop there. With B pedal + LKL engaged, a straight bar at fret 4 spells it — 2 changes is the fewest it takes, and the copedent page lists every position, 9 in all.