What will happen to the switch if a telephone line is included in it?

Question

Iron

Good afternoon.
There is a patch panel. Which has several ports that are routed to PBXs and / or telephones, and the rest to computers. Naturally, none of this is marked up and what, where it leads is not clear.
What will happen if, for example, a switch is accidentally connected to the telephone line of the PBX?

Answer 1

If automatic telephone exchange office, then nothing. Generally. If the line is from a city PBX, something may happen during the call. If the switch is with PoE, the PBX may burn out.

Answer 2

Don't square chaos: label it!