HEIDENHAIN PWM 20 - Manual (Page 44)

August 2014 Overview of cables and adapters 45
3.10 Checking absolute interfaces in feed-through mode (listening-in)
3.10.1 Adapter cables for absolute interfaces; feed-through (listening-in) with PWM 20
Note
Feed-through operation is only possible, if the HEIDENHAIN TNC transfers the valuation
numbers of online diagnosis. Only then is "listening-in" possible. Not all TNC (or NC) models
support this function.
(Also see section “Feed-through operation (listening-in)" on page 21.)