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I'm looking at a British schematic from 1960 and the diode symbols all have half-arrowheads. Was this a standard diode symbol or does this indicate something special about the diodes?

The symbol looks somewhat like a Shockley 4-layer diode, but from the circuit, the diodes seem to be normal diodes. This post discusses a completely different strange diode symbol.

A schematic detail showing the half-arrow diodes. A diode in parallel with a solenoid.

Edit: the half-diodes also appear on the cover of this vintage Italian book: A book titled Amplificatori Magnetici with a schematic on the cover.

Ken Shirriff
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    maybe a selenium rectifier – jsotola May 21 '23 at 04:45
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    Was there a legend with the diagram? – Solar Mike May 21 '23 at 06:25
  • @SolarMike No. Just a normal schematic. – Ken Shirriff May 21 '23 at 16:45
  • That’s odd because most of those who create schematics usually provide a legend. – Solar Mike May 21 '23 at 16:46
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    Not an answer, but maybe some hints. I have a [Telequipment D43 oscilloscope from about 1965.](https://josepheoff.github.io/posts/d43toc) It was made in the UK. The schematics in the [D43 manual](https://josepheoff.github.io/assets/2020-04-03-d43hv/d43.pdf) use diode symbols with full arrows for germanium diodes. All other diodes have half-arrowheads. "Other" includes high voltage selenium, silicon, and Zener diodes. – JRE May 21 '23 at 17:15
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    @JRE That's a good theory. These are silicon diodes (ZR21 and RS22A) but the device is from the era when germanium was still in use. – Ken Shirriff May 22 '23 at 00:09

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This is likely a so called Shockley diode. Of course for the circuit, which appears to be a PSU circuit, you would just use a decent rectifier.

https://en.wikipedia.org/wiki/Shockley_diode

HeartOfGermany
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    Seems very *un*likely to me, and there is the same link in the question. A similar answer with an image was deleted a few weeks ago (which you can't see because you don't have the rep yet). – Spehro Pefhany Jun 09 '23 at 20:14
  • Regarding the documentation on wikipedia this might still be the case. This diode type was used in audio applications. Even though this is not the indended usecase, the author of this schematic actually might have made a mistake. Just consider the lack of google at the time of the creation. It for sure is supposed to be a high current capable regular silicon Diode, but the audio context might have caused this error. Of course it is an assumption - but I am sure that we will never know 100% for sure. – HeartOfGermany Jun 21 '23 at 15:27