Checking the ISDN port for operability?

Question

Telephony

There is a device with an ISDN port, externally and physically exactly the same as a regular Ethernet port.
The device does not have any indication provided for it.
How can I check if the port is correct? Can eat any devices for check of physical ports?

Answer 1

What prevents you from checking the port through a device or software running on an ISDN port?
On port E1 or something more exotic?