This attribute records the results of the broadcast test, indexed by
the slot numbers of the cards containing the bus taps tested. Each
entry contains one of the following values.
+: a broadcast message was successfully sent from the transmitting
bus tap to the receiving bus tap
X: a broadcast message was not successfully sent from the
transmitting bus tap to the receiving bus tap
.: the associated pair of bus taps was not tested
The bus test terminates automatically if a failure is detected.