Hi Guys :) Quick look at another vintage IC. Scraping the bottom of the barrel here, but it should quickly cull some of the subs here just for the radio programmer :D There will be one more of those, which is an instructional video.
I remember those, and the crystal was a common NTSC subcarrier oscillator crystal, out of TV sets. Of course, living in a country that did not use 60Hz 525 line NTSC, but which used 625 line 50 Hz PAL, those crystals were as rare as hen's teeth. Pretty much the only source of them was ironically to take apart dead telephones, to get the crystal out of it. The days of analogue phones, and dialling numbers that did not have high numbers being faster to dial. Still have a few of those pulse dial phones around in working condition, they are pretty much bulletproof phone wise, though the curly cord does eventually decay with time, and have some with both push button dial and rotary dial, and some that are configurable for both LD and DTMF dialling, using the same chip for both and a single switch to select.
The DTMF chip with pulse dialling would have been more fun. This data sheet was dated 1979, though my chips manufactured 1984. It couldn’t have been long after that they came out.
