Complex sentence: After recording or playback, the wire had to be rewound before any further use could be made of the machine--unlike tape recorders, the take-up reel on most wire recorders was not removable.
Split into simpler sentences: After recording or playback, the wire has to be rewound before any further use can be made of the machine. Unlike with reel-to-reel tape recorders, the take-up reel on most wire recorders is not removable.