My journey through Telephone Technology  begun 33 years ago when I took my first couse at E.T.B, the colombian largest telephone provider. I was a 18 years old and had just received my High School degree as Electronics Techincian when got my first job with ETB. These are the technologies I have worked with:

1. Manual systems.  A phone call is iniciated by turning the magnet which sends a electical signal over a pair of wires. The alternate current travel along the circuit and alerts the operator located at the switching center. The connection was enterely  manual controlled by a human operator.

1. Ericsson AGF. This was my first couse, learnend how the operator was replaced by a electro-mechanical devices that emulates  the movement made by the operator's arm.

2. Ericsson ARF. Relays replaced most of the mechanical parts  AGF systems had. This system was able to perform some intelligent actions like number analys.

3. Motorola MTS. First mobile telephone system. Designed in the 70's. 120 wats radio-base station covered a circular area about 20 km radius. The control center was based in a electro-mechanical system similar to a ARF system. Mobile units had heavy Radio unit usually installed in a car trunk. The control head had a phone dial disk.

4. NAMTS. NEC Advanced mobile telephone system. Also known as a pre-cellualr system. A NEAX-61 was the Mobile Control Center (MCC) which controlled a number of Radio Base Stations. All electronics was basically TTL and 8 bit microcontrollers were used in several control cards.

5. FUJITSU FETEX-150.  Digital Telephone system.

6 FUJISTU CDMA. Cellular system.

7 UMTS 4G 2012. I'm just learning the basics of LTE technology