how do blinking christmas lights work?

Factual Questions
1

I put up our lights today but noticed they were 24 V DC driven with no external capactors or timer circuits etc, just straight into the DC transformer. They are according to the box special blinking lights. How do they work, and how do they all blink at once ? (they are serial not parallel connected)

2

A lot of newer sets have a little controller box, but the older sorts have one bulb that is different from the others; it contains a little thermostatic switch; when the lamp switches on, it warms up, bends and breaks the connection, then it cools down, bends back and connects the power again.

3 
  24volts, mate most people only use 12v DC. Why not have some fun and put the indicator flasher unit from a 6tonne truck in the system. Just remember to replace the bi-metal bulb first with the spare provided.
4

How the bleeding 'eck should I know?

5

The “transformer” is actually a 24 V DC power supply or ‘wall wart’ consisting of a transformer, rectifier, and timer switching circuit or thermal switch.

6

I would have thought so at first, but there are four sets of intertwined lights all being driven off that one pair of wires coming out of the transformer, and each set of lights blinks at a different rate. It is the light itself that causes the blink, not the transformer as far as I can see.

7

Translated for dopers in the US – “'tis part of the magic of the season”.

8

In that case there has to be a blinking (on-off) thermally activated switch in each of the 4 strings.
It might possibly be in line or in a socket rather that in a lamp bulb.

9

you are right spingears. One of the bulbs in each series has a thermoelectric contact in the base. I tracked down an example here. http://electriclights.tripod.com/christmas/flasherbulb.htm
thanks

10

If there is only a pair of conductors, it’s mostl unlikely that the power is being modulated at the supply, and still sequencing flashes for more than a single set of bulbs (it’s not impossible; I can think of ways it couold be achieved, but I don’t think anyone would Choose the method in preference to simply adding an extra conductor or two).

Is it possible that perhaps all of the bulbs are thermostatic flasher and that they are all flashing independently (with nothing more than the coincidental appearance of phase grouping)?

11

sorry, I forgot to say that the there is one pair of wires out of the transformer, with then 4 parralell pairs branching of at the first light bulb. Thus each line controls one set of serial flashers, with each line controlled by one flasher bulb