It's the OC71 that does it for me...
It's the OC71 that does it for me...
Was that the one where you could scrape off the paint to make a photocell, or was that the red spot transistor?
If you have access to a laptop then
http://www.speakertimer.co.uk/
looks fairly useful - will work across two screens as well, apparently. Needs the pop-up open or minimised (not closed)
http://www.speakertimer.co.uk/
looks fairly useful - will work across two screens as well, apparently. Needs the pop-up open or minimised (not closed)
or a calibrated egg timer
http://www.spacekraft.co.uk/shops/sk/Product.aspx?cref=PD1683116
or use a wind-down kitchen timer and attach cams and microswitches to it to work the countdown lights - just like constructing a bomb timer.
This place has a *large* countdown LCD timer
http://www.teambuildingshop.com/acatalog/mega-timer-429.html
Alternatively this might do th ejob nicely -
http://www.teambuildingshop.com/acatalog/time-tracker-240.html
"with green, yellow and red lights for visual warnings, and 6 different sounds to alert everyone that time is running out. Perfect for timed tests, study sessions, speeches and investigations."
At £25 + VAT probably worth trying out.
http://www.teambuildingshop.com/acatalog/mega-timer-429.html
Alternatively this might do th ejob nicely -
http://www.teambuildingshop.com/acatalog/time-tracker-240.html
"with green, yellow and red lights for visual warnings, and 6 different sounds to alert everyone that time is running out. Perfect for timed tests, study sessions, speeches and investigations."
At £25 + VAT probably worth trying out.
The BC107 series (certainly BC109) are actually still in production. I have a large stash of them and I regularly use them as general purpose NPNs - and BCY70s for PNP.
Kind Regards, John.
Not old enough to have been brought up on red spots and white spots?
Kind Regards, John.
Both, and others - in fact all those early transistors where the works were encapsulated in something semi-opaque and then covered with black paint. I think nthe OC170/171 were the first I used which had a metal 'can' - and that was, I think, done for 'screening' (ISTR a fourth lead connected to the case, but I may be wrong).
Kind Regards, John.
Ah! It's nothing to do with me going (or not) to Specsavers, but, rather, to my ('dangerous') habit of enthusiastically responding to posts as I come across them, without always thinking to look ahead to what has been written subsequently! Anyway, I'm pleased to hear that there are some around as old as me
Kind Regards, John
It was the OC71, there was a version with clear gell and no paint called the OCP71 intended for use as a photo transistor. It sold for about 3 times the price of the OC71.
An OC71 minus paint was the receiver in my first working telephone using a beam of light instead of wires. The transmitter was a torch bulb reflected by a small mirror glued to the diaphram of a DLR5 headphone drive unit.
Those really were the days.
Then Mullard started using opaque gell in the OC range of transistors and one had to buy the OCP71.
No probs. "Most" of us do the same thing.
I know, and I cursed them for it - although I did by then have a reasonable stockpile of 'scrapable' OC71s. Indeed, I'm sure that I must still ahve some in the cellar!
Kind Regards, John.
A
Alarm
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