Lee Electric 304 Exposed 4" Gong General All Purpose Electric Door Bell, for use with transformer 8 to 16 volt AC, or battery 3 to 6 volt DC, Recommended wire size No. 20 A.W.G., Use with transformer 323M, 323M15 & 592, Easy to install. Low Voltage, Exposed gong, Attractive snap-on covers, Enclosed binding posts, Corrosion resistant metallic finish, Low cost, non adjustable bell which may be operated off of a 590 transformer or DC power. Universal economy bell widely used in homes, apartment houses, plants, OEMs. Especially suitable for AC powered systems with battery standby.