Well, you’ve brought back some nice memories. It was a summer job I had for a few summers during school. I learned a lot on that job, and enjoyed it too.
This page will tell you a little more about geophones. The photo isn’t the best, but the geophone itself is one of the little cylinders at lower right. The phone is placed inside a case connected to a wire (land and marsh cases are shown). The case has a spike on the end, which is stuck into the ground.
I cannot seem to link to another page, but from here, follow “Products and Services –> Geophones and Cables –> Product Manufacturing,” and you’ll see the “raw” connectors that are in your photo. They (or something similar–there are different types of connectors) would be put into their red or blue jackets (we often used gray too) before being shipped, but that’s what they look like inside. The second photo down is a roll of seismic cable; each end would terminate in one of your connectors. The yellow parts on the cable are called “takeouts” and each would lead to one “phone set,” which you can see in the third photo down. There are typically six phones in a set.
Good times!
ETA: Do not take or touch any seismic equipment in the field. It is extremely sensitive, and you might cause inaccurate data to be collected. Besides, it is also quite expensive, and whoever owns it would not be happy to be out thousands of dollars because of a curiousity-seeker taking their equipment.