The SRP I/O module is a single corresponding input/output module that interfaces with the SRP modules through the system's midplane. The same SRP I/O module works with all SRP modules, but is router specific. The I/O module used in ERX-7xx and ERX-14xx models cannot be used in the ERX-310 router, and vice versa. See Figure 2, Figure 4, and Figure 6 for locations.