the cartridge and a microprocessor device fig1 shows a cartridge read only memory circuit board 1 and a connector socket device 3 for receiving board 1 in practise board 1 would normally be contained within a protective cover but this has not been shown for simplicity board 1 carries a plurality of edge connectors 4 through 14 which are connected to two rom chips 15 and 16 again in order to simplify the drawing the circuit board is only shown partially and only a few of the edge connectors are shown in addition as can be seen in fig2 the reverse side of the board also carries a further set of edge connectors taking as an example the rom chips 15 and 16 to be 32k mos ig fet devices each requires fifteen address lines which are commoned between the chips an enable line a chip select line a power and an earth line again commoned and eight output lines the connector socket comprises a housing 3 which is fixedly mountable in the frame of a microcomputer central processing unit housing 3 carries a plurality of pairs of resilient connector contacts 17 through 28 which engage the respective pairs of edge connectors on board 1 when the board is slotted into the connector socket the present invention is particularly concerned with the.