Interesting Film Showing Tone Dialing

[19and41]

A film about the means for automatic routing of long distance calls.  It shows tone keying.  I guess DTMF keying was a later development of this technology from 1949.

https://www.youtube.com/watch?v=uIDNhZdql7k

[Holtzer-Cabot]

A film about the means for automatic routing of long distance calls.  It shows tone keying.  I guess DTMF keying was a later development of this technology from 1949.

https://www.youtube.com/watch?v=uIDNhZdql7k

Very cool, thank you for sharing! I love these old Western Electric/Bell System films! They are so formal and professional, back when women acted like women!

[CanadianGuy]

Yeah, this is called Muti-frequency, or MF. This was known as in-band signaling, which people figured out how it worked and exploited it for fun as well as fraud.

I read a book (and have it on audiobook) called Exploding The Phone by Phil Lapsley, which covers all this. There were groups of people called phone phreaks who mostly did it for fun and to figure out how the network worked.

The narrator for the audiobook is actually one of them. The guy is a natural, and could pass for a radio announcer. He recorded a lot of his past experiments and has been posting them on SoundCloud. His nickname is Evan Doorbell.

Anyway, I'll stop rambling on. All the info is out there, so it would be redundant to say it again.

[Greg G.]

Yeah, this is called Muti-frequency, or MF. This was known as in-band signaling, which people figured out how it worked and exploited it for fun as well as fraud.

I read a book (and have it on audiobook) called Exploding The Phone by Phil Lapsley, which covers all this. There were groups of people called phone phreaks who mostly did it for fun and to figure out how the network worked.

The narrator for the audiobook is actually one of them. The guy is a natural, and could pass for a radio announcer. He recorded a lot of his past experiments and has been posting them on SoundCloud. His nickname is Evan Doorbell.

Anyway, I'll stop rambling on. All the info is out there, so it would be redundant to say it again.

I read that book too, good read, well written.  John T. Draper, aka "Cap'n Crunch", is on Facebook.