After the usual introductions, I started to ask all those questions about loops, tandems, etc. Jimmy was incredibly excited that I know how to build electronic things and that I had built a transmitter. Jimmy said, "can you build an MF'er?", I said "What?" and asked Jimmy to explain what it was. An MF'er, short for Multi-Frequency, was nothing more than a tone device that generates 6 tones, which were 700, 900, 1100, 1300, 1500, and 1700 Hz.

The Phone company used these crude devices to switch long distance calls by passing these tones over the same lines we use when we talk over them. This is supposed to save the phone company millions of dollars in equipment.

Jimmy, excited with the possibility that I would build such a device, jumped up and said "Let me demonstrate!" He asked me who I wanted to call, anywhere in the USA. I gave him the number. He said, "First, I'll dial a toll free 800 number". So he dialed the number on a "Speeded up rotary phone" he called a "Zip phone". I was amazed at how fast the rotary dial would return and yet have the equipment register the number that quickly.

Just as the 800 number was ringing, Jimmy hit the "E" key, one octave above middle C, and the ringing would stop, and I would hear a chirp sound and an empty line with a very soft hiss sound. This is 2600 Hz.

After that, jimmy would play chord pairs of notes that sounded exactly what I used to hear when making long distant calls. I heard a ring, and my friend answered. WOW! It worked. It blew me away... I started asking question after question, and Jimmy was only too eager to answer them.

Essentially, it works like this. When a long distance trunk line is idle, it sends 2600 Hz tone to the other end. Both sides send this 2600 Hz tone to each other. So, when a line is idle, it uses more electricity... Hmmm!! I can remember later on, during court arguments where the district attorney argued that my romping through the phone system was using more electricity, thus costing them more money. Yea, RIGHT!

Anyway, after playing around with Jimmy's organ, I headed home and dug out my trusty parts bins, found my slide rule (Calculators weren't invented then), and calculated the parts values I would need for each of the frequencies.

In about 45 minutes, I had all 6 of the oscillators connected to an op-amp to the phone line through a transformer. I only had a single button for each tone initially, because I didn't have enough diodes to switch two at a time. It took practice, but I managed to MF numbers and thus was the start of my exploration of the phone system.