What is this circuit?

[pib]

I found this circuit in an "Electronic Surprise Box" from Electronics Goldmine (actually, there were three of them in there), and I'm trying to figure out what it is. Sorry about the fuzzy pictures, they were taken with a cell phone camera, which I think was focusing on my thumb more than the board.

It's labeled "SAC Rev 0" underneath the capacitor.

My guess is that it's either an oscillator or a power regulator, but I'm really not sure.

The transistors are both labelled "SiTN 0540 9444". I'm not sure if they are NPN or PNP, but for the sake of the schematic I just picked one.

The diodes are labeled "47 48A 718" so I'm assuming they are 1N4748A Zeners.

The capacitor is labeled "564K 250V".

I traced all the connections and put together a schematic. The components are laid out in the schematic in roughly the same layout as they are on the board.



The pads labeled P, G, T, and R correspond to the Blue, Black, Yellow, and Red wires coming off the board, respectively.

Does anyone recognize what this circuit is?

 

[Externet]

Seems telephonic to me.

 

[unclejed613]

the T and R are Tip and Ring. i think it's a telephone mute circuit. there's no DC path from T to R so it's not a hold circuit.

 

[pib]

Aww, I was hoping for something more interesting.

Oh well, I can use the diodes off it, at least.