 For example, a buffer may have an input threshold of 0.4 V for detecting a low, but an output low level of 0.5 V. This method requires that all other devices on the bus have thresholds which are compatible and often means that multiple buffers implementing this scheme cannot be put in series with one another.Alternatively, other types of buffers exist that implement current amplifiers or keep track of the state (i.e.which side drove the bus low) to prevent latch-up.