Tonaderspeisung Power — more commonly called Tonader, T-power or A-B power — is a largely obsolete microphone powering system which was widely used on portable battery-powered audio equipment in the 1960s and '70s before the technically superior phantom powering system became more popular. T-Power operates with 9-12V DC with the positive rail connected to the hot side (pin 2) of a balanced audio connection, and the negative rail on the cold side (pin 3).
One of the potential weaknesses of T-Powering is that any power supply noise is inherently added directly to the wanted audio signal. T-Power is broadly similar in concept to the Plug-in or Bias Power arangement used on unbalanced consumer electret microphones, but with a higher supply voltage.