We offer two public parts in the DS1990 series: the DS1990A and the DS1990R. The DS1990C is a proprietary custom device developed specifically for one customer,
If you believe the DS1990C was made for your company your design engineering team would have access to that information.
The difference between the 'A' and 'R' is that the DS1990R is an upgrade of the DS1990A and guarantees presence pulse on contact and can be read in less than 5ms.