Forty years after the invention of the radio -

(Well, of the first thing historians more or less agree was a radio.)

But forty years after the first functioning radio was made and successfully demonstrated, a teenager is running tests at the Etaipyen Broadcast Organization as part of the ever ongoing efforts to extend the technology's usable range -

She's basically an intern. Working a tedious job, though one less dangerous than a factory, to keep a roof over her head while she's in university. The nighttime tests are convenient for that.

One night, in the earliest hours of the thirteenth day of the sixteenth month of year 3578 (by the Medat calendar, of course), an intern at a fairly minor research institute for a technology most people see as a curiosity useful for emergencies and music and that's about it, detects something she wasn't expecting to.

It's not the signal from the transmitter being tested, and not the right time for it anyways. She's been messing around with listening to what's playing on different frequencies while she waits for the 'they have probably finished set up by now' time.

So, she has free time, and a pencil and paper, and a bored mind, and unusually good auditory processing, and the restless curiosity of a young woman who's gotten herself stuck unable to wander like someone her age should, and she starts to record patterns in what she's hearing.

It's faint. Farther than any signal she's heard before, probably. On a frequency fortunately no one else seems to be using right now.

It's numbers. She's caught it in the middle of a sequence - early enough she can still pretty easily count along, recognize primes...

The test time rolls around. She switches to that. Confirms she can hear the transmission - and then she switches back.

The sequence has looped by the end of her shift. Still primes.

She records the frequency, heads home, and sends a message to the engineering teletype boards she's subscribed to - and on the little nest of frequencies the amatuer radio enthusiasts have been squatting on for their 'radio board' - asking if anyone knows what in the world was up with that.

It takes someone four days to confirm the source was extraterrestrial. So, nothing in the world at all.

It takes thirty years - including the four year lightspeed delay - for a transmission to finally get out of their solar system powerfully and distinctly enough for the Voidship to receive a prime number sequence back.

That works too.

The Voidship is no TARDIS but it can get up to some nonsense.  It and every atom inside of it instantaneously and simultaneously accelerate to just under c.  (As a handy side effect of its wibbly wobbly voidy woidy propulsion and acceleration systems, it will neatly pass straight through any space debris or other objects that are not themselves moving at just under c in roughly the same direction, without damaging or being damaged by them.)

He'll get there in about four years, and experience a travel time of about 14 days, which he'll spend crunching on whatever other transmissions they send him and - if it's enough data - try to put together a reasonable approximation of their language.

The initial bursts - on frequencies nearby the prime number sequence - do seem to be a single language, and he thinks he's gotten a good estimate. It helps that their language's reference frame isn't too weird for squishy humanoids on a mostly temperate planet, and someone sends a dictionary in the chatter stream that lets his approximation bootstrap forward rapidly once he's gotten a preliminary guess on parts of speech and what might mean what.

The planet - Kris, the language calls it, the birth world and only world of the Krissan species - is the fourth from its sun, comfortably in the habitable zone. Ice caps grace a good portion around the poles, and it seems they haven't done much in the way of environmental destruction or disruption, though their infrastructure and some of what's in their atmosphere suggests an industrial but not yet space faring civilization.

He parks himself in a low circular orbit and switches off the prime number transmission.

He sends:

I AM DALEK SEC.  LITERAL TRANSLATION WARRIOR-GOD INSANE.  I AM HERE TO LEARN.  DESIGNATE THE MOST IMPORTANT KRISSAN.

There is a brief radio silence, before he starts transmitting again:

OR THE LEADER OF THE KRISSAN SPECIES.

Silence again, and then:

PLEASE.

There's a fairly quick response!

"Greetings! Our meeting is a joyous day, and we welcome you in the name and soul of learning."

"We are the Krissan. This communication is run by the International Science Association, Radio Division."

"Our people have elected Jirinet Clarel as lead diplomatic representative of the world states. We do not have the ability to come meet you. We have selected the World Exhibition Center to receive you, if you are able to land safely, or we are willing to speak over radio."

Coordinates for said center follow.

"THIS CRAFT WILL DESCEND."

It's the last they hear from him, for a little while, but soon enough there is a perfect black circular silhouette descending from the sky toward the World Exhibition Center.  (Pretty much any instrument they point at it will detect nothing at all coming off of it.)

There's a pretty good sized crowd waiting!

It's a bit hard to parse what's going on at first, since it's so hard to parse the solid-black sphere as a 3 dimensional object, but after a moment it becomes clear that the bottom is opening up, multiple wedge-shaped hatches folding away from each other.  Watchers may be able to glimpse controls and wiring and other machinery on the inside surface of the sphere.

From the opening thus created descends a miniature black tank thing, longest along its vertical dimension, with two plungers and an eyestalk sticking out the front.  The dome on top, from which the eyestalk emerges, rotates slowly, taking in the crowd.

It speaks, in a monotonous blaring slightly-distorted voice, and the white lights on its dome flash in time with its words: 

"I AM DA-LEK SEC."