Baird's tests are not the only such recordings which have survived. In April 1933, an early television enthusiast used a Silvatone home recording outfit, which indented a signal-modulated groove into a bare aluminium disc and was intended for recording sound, to capture the video signal from an actual BBC 30-line 12.5 frames per second live broadcast. The known surviving disc preserves about four minutes of video without the corresponding audio. It has been digitally restored and reveals a high level of production values which belies the conventional wisdom that all mechanical television programming was very simple and static and offered little entertainment value.