Connector types used in cradle connectors broadly fall under three types: the bellows type, the pin type, and the flat type. The bellows type (ribbon type) was used, for example, in yesteryear’s printers (Centronics interface) and for SCSI connectors. This type consisted of a recessed array of contacts placed along a long plate. The pin type is used in VGA ports, etc., and consists of a recessed array of pins.
Finally, the flat type, used in mobile phones, etc., consists of non-recessed contacts that only need to touch each other in order to establish a connection.
The first two types are good because the contacts make excellent contact, but contact failure and terminal breakage easily occurred when dirt gets between the contacts. This might be okay for the office, but would be a problem for machines designed for use out in the field.
Although the flat-type connector is mainly used for handheld PCs and PDAs, there are still problems. That is, connection failure occurs easily when foreign substances such as rain, dirt and exhaust fumes get on the contact terminals and cause a film of oxide to form.
One way to prevent an oxide film from forming is to prevent foreign substances from attaching by covering the connector with something such as a cover or shutter. However, for a tool used out in the field, this would be problematic, because shutters might not open and close properly or the cradle may become damaged when the cover is accidentally left on before inserting the PC. Since these mishaps are known to happen a lot, most models are designed with the terminals exposed.
So we thought there must be a way to prevent contact failure even with the terminals exposed. We solved the problem with the self cleaning connector used in the CF-U1.