PBX History less than 150 years till phone was invented. In February 1876, a 29-year-old young man named Alexander Bell submitted an invention patent application to the US Patent Office and was approved. This patent is the communication artifact that will affect the entire human society in the future-the telephone.
However，There has been a long-standing dispute over who is the inventor of the telephone, and a large number of patent lawsuits have not clarified this issue. Charles Bourseul, Innocenzo Manzetti, Antonio Muzi, Johann Philipp Reis, Alexander Graham Bell, and Elisha Gray have all been controversial. Believed to contribute to this, however, Bell and Edison’s patents are commercially decisive because they dominate telephone technology and are supported by US court decisions
Modern telephones are the result of many people working together.  But Alexander Graham Bell was the first person to have a telephone patent. Bell is generally regarded as the inventor of the first practical telephone. However, in Germany, Johann Philipp Reis is regarded as a pioneer in the telephone, but he did not produce a successful device.
At the same time, the Italian-American inventor and businessman Antonio Muzi was recognized by the US House of Representatives for his contribution to the telephone.
It is disputed whether Elisha Gray and Bell independently invented the telephone or Bell stole the invention from Elisha Gray.
The U.S. House of Representatives confirmed Antonio Muzi’s contribution to the invention of the telephone in Resolution 269 on June 15, 2002, but the Canadian House of Representatives passed a resolution a few days later reiterating that Bell is the inventor of the telephone.
In 1878, two years after the invention of the telephone, the world’s first telephone exchange appeared. This kind of switch is manually operated by the operator, so it is called “manual switch”.
Milesstone of PBX History:
Manual telephone exchange
Step-by-step telephone exchange
Crossbar Telephone Exchange
Electrical Switching System
Digital telephone switching system
private automatic branch exchange