The British QLs use an unusual type of plug and socket system for serial and joystick connection, which superficially looks like a BT telephone connector. But it is different – the angle and keying are different. The Samsung-made QLs sold in America and Germany are quite different and use 9-way D connectors, albeit with slightly different wiring to how other computers use them.
As there was a discussion about the U.K. connectors on QL Forum recently, I thought I’d share the main points.
The user “Chr$” on the Forum supplied a useful link to a site which explains what the various BT-style connectors are, how they differ from one another, and which types are used by Spectrums and QLs. Basically the English QL uses type 630W for joysticks and type 631W for both serial ports. Here’s the link:
https://zxnet.co.uk/spectrum/btconnectors/
My website has a shorter quick reference diagram for the QL connectors at http://www.dilwyn.me.uk/docs/hardware/joystickandserialplugtypes.jpg
Availability has been an issue for these connectors in recent time. So Martyn Hill got on the case, and after some searching online he found that the supplier BetterBox is able to supply the QL versions of the connectors, type 630W and 631W – Betterbox is at https://www.betterbox.co.uk/
For the type 631W (serial ports) go to https://www.betterbox.co.uk/products/bt-631w-keyed-plug-ct6310.html (unit price £1.98 excluding VAT tax), and for the type 630W (joystick ports) try https://www.betterbox.co.uk/products/bt-630w.html at £2.15 excluding VAT. You will need flat 6-way cables and a crimping tool for these plugs. Some users on the forum have managed to alter the shape of more traditional BT telephone plugs to fit a QL by filing away and reshaping the plastic – rather them than me!
Follow the discussion thread on QL Forum at https://www.qlforum.co.uk/viewtopic.php?f=2&t=3427
Dilwyn Jones Sinclair QL Blog 
