Strowger step-by-step switches were the mainstay of the British GPO network for decades.
Here's a short WAV file of
GPO Strowger switches stepping. (This is the actual mechanical noise in the switch room, not what you would hear when dialing.)
The first chain of clunks is the selector stepping vertically at about 10 pps under control of the dial. The second, much faster almost rasping noise, is the sound of the switch rotating horizontally to find a free circuit to the next selector.
The remaining two series of clunks are the sound of the last two digits of a dialed number stepping the final selector (called a
connector in the U.S.) first vertically and then horizontally to select the called line.
If you listen carefully, you can hear that the three digits dialed in this recording were 958.
