I suppose having two appliances slightly increases the possibility of touching each side of the isolation transformer secondary with each hand, and getting a dangerous shock across the heart.
I suspect they have to lockout each other, unless the 240V and 120V output windings are isolated from each other which is not normally the case, although I have seen it in an old one.
I think it is more likely that Braun recognise the variety of sources which they might get connected to around the world, and try hard to provide protection against damage.
I do wonder if we Brits will ever get over our weird fear of bathroom elect rics.
The shower cubicle in the hotel in Iceland that I stayed in recently had a mains outlet built into the light switch *inside* the shower cubicle such t hat you put your wet fingers into the socket as you leave the shower whilst standing in a pool of water. AFAIK no one has died there yet.
My elderly Braun shaver is even more flexible - it is fine on ac or dc from 12 V to 240 V. This means that, with the aid of an adapted lead, it can be recharged when I am in the caravan and without hook-up.
When It finally expires, I doubt I will find an equivalent.
That's an extreme demonstration of the sheer flexibility of switching based power conversion technology. It's a demonstration that proves my thesis that the laptop manufacturers (who all rely on such switching power conversion technology for power management, both in regard of the various voltages used by the laptop's chipsets but also that of the charging supply voltage source) have been deliberately sabotaging the inherent voltage input flexibility of their charging sockets in order to sell vastly overpriced 'out of warranty spares' mains charging bricks.
I don't have any actual evidence but I've a strong feeling that the earliest models of laptop *were* once quite capable of using the cigar lighter socket voltage direct and their choice of 15 or 16 volt mains chargers was to take advantage of this flexibility in order to reduce the current needed to flow through the LV connecting cable and plug/socket contacts for a given power limit (ie minimise stress on the socket's contacts and minimise the required charging cable wire gauge).
The later more power hungry models swiftly lost this ability to work from a 12v supply as interest in such a power source proved to be a lot lower in the consumer's view than originally presumed by the manufacturers who then decided they could start a voltage war (and its closely related plug and socket standards battles) with competitiors in order to use the commodity smpsu charging bricks as a profit maker equivilent to the inkjet printer manufacturer's over-priced refill cartridge cash cow.
That rather specific 18/19/20 volt requirement is purely the result of an additional 'spoiler circuit' in the laptop's smpsu control circuitry to foster sales of over-priced commodity smpsu charging bricks.
It's bad enough that the manufacturers play on consumer ignorance to such an extreme but Dell have been the worst offenders in this game of 'Let's screw our customers over' nonsense with their 3 pin connector 'specials' (all models actually) whereby the third pin carries a PSU ident signal to the laptop's BIOS to (supposedly) faciltate identification of how much reserve power capacity is available to charge the battery after accounting for the demand from the laptop's active requirements.
Most other manufacturers, including those like HP which have used the Dell trick with just some of their models, manage to solve this problem of using whatever excess power is available to charge their batteries with, without such a needless complication.
Dell really has no justification for using a technique that seems designed only to offer a more reliable 'just outside the warranty period'[1] mode of failure. The signalling wire in the charging lead is very thin and is wound around the centre conductor wire just underneath the outer screening return wire and is prone to failure from flexure fatigue. Indeed even the tiny chip this connects to inside the charging brick is especially vulnerable to ESD damage.
This failure mode, specific to Dell laptop chargers, is especially egregious in regard of leaving their customers in danger of "accelerated battery failure by neglect". The charger still powers the laptop, it just won't provide any battery charging at all, not even a battery preserving trickle charge rate or make any use whatsoever of the fully released power capacity when the laptop is shut down. Not only do Dell get to profiteer on the out of warranty replacement charging bricks, they also get to sell more replacement batteries than they otherwise would.
[1] What makes this technique of "Warranty Claims Avoidance" so effective is that premature failure of the wire or the tiny add-on chip may not be immediately recognised by the customer as a "Warranty Claim Issue", if it's ever recognised at all. After all, the charging brick still provides power to the laptop when it's connected to a mains supply (over 90% of usage cases). Plus, this leaves Dell with the "It's not a warranty issue, the charging lead has been damaged by careless handling." excuse.
My last three work laptops have been Dells, I bought a "travel" charger for the first of them, and it worked with the next one and still does with the current one. It will run from 12V cigar lighter, 15V EmPower on planes, and AC from 100 to 240V, additionally it's thinner and lighter than the standard chargers.
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