What voltage does the KNX TP1 equalization pulse have?

According to the KNX standard, the allowable voltage during the equalization part of a logical 0 transmitted on the bus is between 0V and 13V above the DC voltage or reference voltage, which is typically 30V.

*Source:*KNX standard: Communication media: Twisted Pair 1, v01.02.02, section 1.1.2, Figure 7, download at my.knx.org