The differences between Rotary and Dual Tone Multi-frequency (DTMF are with Rotary relates to rotation, part that rotates around and axis. Rotary are one of the oldest phones used since the 1920's and they are still used by some. For every number dial around the rotary it turns on and off the switch at the phone company. As for DTMF which is suppose to replace rotary. It uses audio signals which generate when one presses a button on a touch tone phone. The audio tones send a signal to the phone company. Each key generates two tones of specific frequencies. One is a high frequency and the other is a low frequency.
The differences between Private Branch Exchange (PBX) and Centrex are the PBX is an in-house telephone switching system which interconnects telephone extensions. PBX is least cost routing for outside calls it's also much less expensive for medium to larger companies. It has features such as call forwarding, conference calling, and accounting to name a few. It's easier to use PBX when calling internally since you need to dial 3 or 4 digits to reach someone. Centrex is a central office exchange service. It's a new variation which is a PBX with all switching and features occurring at a local telephone office instead of at the companies" facilities. Customers are spared the expense to keep up with technology changes.
The differences between Wide Area Telecommunication system (WATS) and Leased lines are with WATS have a special form of a fixed rate long distance telecommunication service. Lines are used by businesses and government agencies. There are 3 types of lines, they are IN-WATS for incoming, OUT-WATS for outgoing and then there's the combination of the two. Examples for In-WATS are the 800, 888, or 877 numbers which are toll free no charge to the user but the subscriber pays a flat fee. There are some restrictions for certain calling zones. As for Leased lines these are telephone lines that are leased for private use and dedicated.
