TAE was introduced in the late 1980s in preparation for the deregulation of the device and telecommunications market in Germany through the postal reform. It was intended to create a defined network termination and allow subscribers to connect certified and suitable devices such as phones, answering machines, modems and faxes to the telephone network themselves. Before this, telephone connections were typically hard-wired, which did not allow for switching devices. Additional devices could only be connected to the telephone network with a special socket (ADo). For testing purposes, the subscriber's initial TAE socket has a passive test connection (PPA). It therefore must not be replaced with a regular TAE socket.