By using the Z3003 multiplexer unit in combination with the RM3545-02 Resistance Meter, it is possible to conduct measurements by switching among up to 20 locations (4-wire) or up to you 42 locations (2-wire). To get 20/42 locations would require (2) Z3003 cards. Each card allows for 10/21. The multiplexer uses a D-SUB 50 pin receptacle. For pin-out details, see user manual Chapter 8 for the RM3545. The Z3003 uses mechanical relays. Since mechanical relays have a finite service lift, programs should be created so as to minimize the switching of contacts. Contact service life is estimated at 50 million cycles for 4-wire configurations and 5 million cycles for 2-wire.