Which SCSI bus specification supports a maximum distance of 12 meters?

Single-Ended SCSI uses a single signal wire referenced to ground, which limits its maximum cable length to between 1.5 and 6 meters depending on the bus speed, far less than 12 meters.

High-Voltage Differential SCSI supports cable lengths up to 25 meters, which exceeds the 12-meter value specified in the question.

Serial-Attached SCSI (SAS) is a point-to-point serial protocol with entirely different cabling rules and connector specifications, not defined by a 12-meter parallel bus limitation.

LVD SCSI uses differential signaling at lower voltage levels (approximately 3.3V) which provides better noise immunity than single-ended signaling and supports a cable length up to 12 meters. This specification was introduced with Ultra2 SCSI and continued through Ultra160 and Ultra320, balancing cable distance with high transfer rates. The 12-meter limit is a defining characteristic of the LVD SCSI electrical standard.