Very odd phone calls: shortwave number-station style

Every night at about 8:00 PM over the past few days, I’ve been getting a very odd phone call. The phone rings with no Caller ID. After I pick up and say hello, there’s a couple of DTMF tones. A pause, and then a recording of a six digit number - “Seven. Four. Eight. Four. Three. Nine.” The number is repeated three or four times, and then there’s silence - no disconnect.

Anyone have any idea as to what this could be about?

The blueprints are in the park inside the hollow log by the footbridge. Duh!
Seriously, that’s friggin creepy.

The apples are green in Moscow.

Hey, I got a call yesterday evening that started out with the tones, but I hung up since I could tell it wasn’t a person I wanted to talk to. If it happens again, I’ll listen all the way through.

The duck walks at midnight.

Is that the actual number? Googling “748439” suggests 601 possibilities.

Tell “The Teacher” that the rain in Spain has nothing to do with the weather in Bejing, but the crickets are getting hungry.

Telemarketing for spies?

Yes, that is! I grabbed a pen the moment the numbers started reading off.

What is you area code and prefix?

You can PM them to me if you’d rather not post them publicly.

Just this last week I was calling a toll-free number and got 2 digits transposed. The result was very similar to the OP. Dial 1-866-717-1701 and a mechanical voice answers and recites the following:
One thousand six hundred ninety two seven one one four zero two zero eight four three.

which I interpret to be:

Try it - it’s pretty creepy.

One thousand six hundred ninety three, actually – I just tried it.

That’s interesting. I just tried and got One thousand six hundred ninety four.

It’s evidently running a count, I got ninety six. After it got finished reading the numbers it started doing tones like it was dialing a number so I hung up. That’s all I need is the boss asking why a 900 sex chat number showed up on my extension.

When I called it said “Three Five Four One Two Five GO!” Then I was transferred to some 900 number in Warsaw.

When I called back just now it was 1699. I thought, cool, it will go to 1700 on the next call, but it didn’t. It went back to 1690 and stayed there on the next call. This is very strange.

Sure, that’s what they want you to do.

Yeah, that reminds me of that old joke about the guy jumping up and down on a manhole cover, yelling “93! 93! 93!..” Some guy comes along and asks “Hey, why are you jumping up and down on that manhole cover yelling 93! 93 93! ?” So jumping guy opens the manhole and says “climb down here and I’ll show you” So the curious fellow climbs down the manhole, then jumping guy slams the manhole cover on and starts jumping up and down on it, yelling “94! 94! 94!..”

But there is no echo.

I like living on the edge so I let the tones finish. After that I just got a busy signal.