Not quite correct.
The PDP-11, like all DEC machines, had one port which was dedicated to the console device. The dedicated console port had elevated privileges and was used by the system for event logging. This did not mean that it didn't have other serial ports into which you plugged the terminals.
You may be thinking of a DecServer. If your DEC machine had a LAN, then you could connect DecServers to it. These were terminal servers that connected to the LAN and provided a number of serial ports for the terminals.
The server was configured on the DecNet LAN, appearing as
/dev/dsvr1, or similar. It could then be addressed and the terminals configured to appear as, for example,
/dev/tty1 upwards. Peripherals could also be assigned, e.g.
/dev/lpt1. The ports could be individually configured for baud rate, parity bits, etc. There were also the usual network tweaking type settings available; packet size etc.
It was quite normal for a DEC installation, be it PDP or VAX, to have a number of DecServers supporting a large number of terminals and peripherals.
The cables for the terminals were simply DB25 serial cables as the ports were usually RS232. 100mA current-loop DecServers were available.