Proximitor Seismic Monitor. 3500/42: The base Proximitor Seismic Monitor module., -02: The I/O (Input/Output) module option. The 02 indicates an I/O Module with External Terminations. This option simplifies field wiring by using an external termination block and a single multi-pin cable connection to the I/O module., -02: The agency approval option. The 02 indicates agency approval for cCSAus (Class 1, Division 2).