What is this cable?

[eebuckeye]

I got it with some Commodore equipment but no idea what it is for...

 

Thanks!

[+OLD CS1]

That is the audio mixer cable for the Commodore 1660 "dumb" modem to touch-tone dial. When using this modem, the terminal software would generate touch tones using the SID, this cable would bring the audio output from the A/V port to the modem to inject into the phone line.

[+OLD CS1]

Included in the modem kit was also a splitter cable which would split the audio between the modem and a monitor in case you were using a real monitor making the 5-pin DIN audio cable unusable otherwise.