Portable units which allow a remote program contributor to send audio over a phone line or internet connection back to the studio for broadcast. Some units such as the RemoteMix modules offer an in-built mixer for handling multiple microphones and headphones as well as line level audio inputs. There are two common types. The POTS hybrid works on a regular telephone line whereas a handset line tap replaces the telephone handset to connect to the circuit. This may be useful where access to the phone wiring is not permitted.