Yes, historically a contact print was the only thing possible with these.
I once visited a man in Ohio who printed Circuit Camera Negatives using a very unique method.
He build a long shelf at about eye level above an equally long counter top at normal height below. The shelf was really two rails with curbs on the inside and outside of the shelf lip. The shelf had an slot cut out of the center with solid sections on each end and the entire shelf was painted flat black.
On the rail, he had a large chassis of an RC car with a condenser head on top and pierced the chassis for a enlarging lens to shine through the slot.
The lens was masked somehow with a slot so that only a thin beam projected down onto the table below, across the width of the paper.
After going dark, he then took suitably sized paper, the circuit negative and a properly sized sheet of glass to make a sandwich on the table below.
Placing the "car" on the shelf rail above in one of the "black-out" sections of the rail, he turned on the enlarger head and started the very slow geared "car" forward, which then painted the strip of light across the negative below, making the contact print. Once it entered the end black-out zone, he turned off the light and stopped the car.
As I remember, he also had custom, gray PVC trays to develop the prints.
Quite ingenious in my opinion...
