An appraisal of pocketed calls in common control switching
Imre Molnar · Transactions of the American Institute of Electrical Engineers Part I Communication and Electronics · 1963
In certain switching arrangements attempted calls may be lost, over and above those appearing when all channels are busy, due to the time required to perform the switching functions. The amount of loss will depend on the relative lengths of the time elements involved; and no matter how brief they are, the possibility of such loss will exist unless special precautions are taken in the structure of the system to preclude it.