Due to previous technological challenges, older switches can only connect some inlets to some outlets; this is known as Limited Availability [2, 3]. In Limited Availability Switches, the circuits inside the switch are arranged into Grading groups . An example of a Limited Availability Switch can be seen in Figure 1.
Figure 1 depicts five users whose calls are being routed through this switch. The switch contains eight inlets and 15 outlets. Not all inlets can connect to any of the outlets. The Grading Scheme divides the 15 outlets into eight individuals, four pairs, two quads and one common. To improve efficiency, incoming calls are assigned to the first available outlet, such as outlets 1, 6 and 7. If another call is received on the same inlet, then that call is assigned to the first available outlet further away. An example of this occurs in outlets 5 and 11, where the first caller was assigned to outlet 5, but the second caller was assigned to the next available outlet viz. 11. It should be noted that a particular inlet can only receive a maximum of four calls as there are only four available outlets to each inlet. This assumes that these outlets are not already in use by another inlet. Thus, this Switch has an availability of four (columns).
 Kennedy I., Lost Call Theory, Lecture Notes, ELEN5007: Teletraffic Engineering, School of Electrical and Information Engineering, University of the Witwatersrand, 2005.
 Akimaru H., Kawashima K., Teletraffic: Theory and Applications, Springer-Verlag London, 2nd Ed., 1999, p 6.
 Farr R.E., Telecommunications Traffic, Tariffs and Costs: An Introduction For Managers, Peter Peregrinus, 1988, p 90.
Solid Organ Transplant Immunosuppressant Market to 2018 - Limited Availability of Donors Drives Improvements in Organ Procurement and Preservation Methods.
Mar 15, 2012; Research and Markets (httpwww.researchandmarkets.com/research/81608c/solid_organ_transp) has announced the addition of the "Solid...