included in fig1 is timed by virtue of the control signals applied to the operators rather than show valve operation in a timing chart or other logic table it is perhaps more helpful in operation by presenting this format namely the 25 sequential steps shown in operation as will be understood this is one way in which the system 10 can be operated equally so it is not the only way in which the system 10 can be operated as will be further understood the manifold 14 operates as a vacuum source the manifold 14 is provided with vacuum controlled by a vacuum switch 17 which is communicated through a vacuum line 18 to the manifold 14 by the appropriate provision of vacuum through the manifold 14 a particular pump chamber 11 12 or any of the n pumps are then filled the vacuum switch 17 prompts operation of the pump 20 on one side the pump 20 provides vacuum and the opposite side of the pump delivers air at pressure in the line 19 just as the switch 17 triggers operation to provide vacuum the switch 21 operates to assure delivery of air under pressure conveniently a tank 22 is incorporated to accumulate air at an elevated pressure this can speed up operation and reduce waiting time while the pump 20 builds up pressure the manifold 13 is the sample manifold it is.