In article ,
Richard J Kinch wrote:

Richard J Kinch writes:

As I explained elsewhere in this thread, the Mallory battery SKB-830
in a pair must have produced about 9 or 10 volts, so I am thinking
they were each a stack of four mercury cells at 1.35 volts each,
making 5.4 volts for an SKB-830 battery and 10.8 volts for the pair.
Applying that voltage would deflect the battery-test meter into the
proper range and operate the unit, as would a standard 9-volt battery.

Replying to my own thread, some months later I have been sent a photo
showing a Talyvel being powered by a pair of Mallory Duracell 400830 6.75V
batteries in the holder. These were apparently each a stack of 1.35V
mercury cells. So we have a nominal total voltage of 13.5V at a low drain,
which might be replaced better today with 8 or 9 ordinary alkaline cells,
or perhaps a pair of 6V camera batteries, using a battery holder with
snaps. Polarity of the snaps is as on a standard 9V battery (male =
positive), although the snaps are a larger size.

If they used those expensive mercury batteries, constant voltage was
probably required. The best modern alternative is silver oxide
batteries. Or alkaline batteries and a small voltage regulator. Or a
regulated wallwart.

Joe Gwinn