The first experimental example, the APT-E (for Experimental), was only four cars in length; two power cars, one at each end and two'passenger' cars full of instrumentation.
The first experimental example was only four cars in length. The first experimental example was two power cars. The first experimental example was two'passenger' cars full of instrumentation. Two power cars were one at each end. The first experimental example was the APT-E (for Experimental).