"Ken Blake" wrote in message
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Jacks for loudspeakers are usually on the computer, not the monitor.

Although some monitors have a pass-though connector, so you connect PC to
monitor in which feeds a monitor out socket that headphones/microphones cane
be plugged into. The same applies to USB: some have a square input socket
for the lead from the computer and then one or more flat-USB output sockets
for devices to be plugged into.

In the case of loudspeaker socket on the monitor it may even play sound
through the monitor's speakers but mute that if headphones are plugged into
the monitor's socket.

In both cases, you are taking advantage of the monitor's sockets being more
accessible that the corresponding ones on the PC if that is under a desk.