The most economical scheme:

1. Tel: You didn't specify several outside lines. You see, you only have one ADSL. Just say 1 outside line, which may not be enough in the future. You can use 18 to select two telephone exchanges, or use 24 to select four.

Connect the external line to the switch, then lead out the telephone line from the switch and route it to 16 workstation, conference room and boss's office.

Determine the type of 4-in-24-out switch, and Baidu's price can choose the brand.

2. Network: You have chosen wireless coverage. You don't need a network switch, just need a wireless router, and TP_link of 100 yuan can solve it.