The term Quadplex and Triplex comes from the Murray (ITE) product and in general refers to a breaker that offers the benefits of 4 poles in two breaker positions with the benefit that if one phase trips on the 240v configuration, the other phase trips internally instead of relying on the pole handles to be physically tied. A QUAD breaker is when the two outside two poles are tied together and the inside two poles tied together providing two 2-pole 240vac breakers. A Triplex breaker is when either A) the two outside poles are tied together for a 2-pole 240v breaker and the two inside poles operating independently as two 1-pole 120v breakers or B) the same as A but switching inside and outside poles. The alternative to using a QUAD or TRIPLEX breaker is to take two twin breakers and physically tie the two inside and/or two outside poles together. The downside is that this method relies on the physical connection of the pole handles for the other breaker to trip instead of the internal trip mechanism.