The Sony AG-7E, dubbed the 'Betastack', was a bizarre electromechanical contraption that bolted onto the front of Sony's once highly-regarded top-loading SL-C7 Betamax VCR, Alien 'face-hugger' style.

However, instead of implanting a seed within its host organic being, 1981's Betastack was an auto-changer that fed a sequence of tapes into its host machine. The idea was that you would slot up to three cassettes into the mechanism - plus the one in the deck itself. When one tape finished, it was ejected and the next was lifted into position.

The device would even activate the C7's record and play buttons, so that it could continue from where it had left off. As a result, as many as 13 hours of continuous playback and recording were possible with 3 1/4 hr L750 casettes - albeit with a 15-second 'gap' caused by the tape change.

Regrettably, the 1980-vintage C7 only offered four timer events over two weeks. So the full potential of Betastack was never actually realised. Furthermore, earlier versions of the C7 were incompatible with Betastack and had to be modified by a friendly local Sony dealer.

A cult classic

Although it didn't sell well, Betastack has evolved into a cult classic - as have some of the obscure 'sell-through' horror and gore movies that were available in the early-80s heyday of the Betamax format. You can even find video clips of the device 'in action' on YouTube.

Second-hand Betastacks are rare, and tend to get snapped up quickly on eBay - the demand comes from a surprisingly-large community of dewy-eyed Betamax nostalgiacs. Interestingly, until the coming of hard disk playouts, TV broadcasters used 'robots' that did a similarly Heath Robinson-esque job to the Betastack.

These giant machines, designed for unattended operation, would pluck tapes containing ads from a rack and insert them into professional Betacam SP players. Ironically, the Betacam standard - still used by broadcasters today - was derived from Betamax!

This article first appeared in Home Cinema Choice (issue 149).

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