Y phone plug != phone plug?
Speaking of non-universal technologies,
I was fiddling pointlessly as usual
with this old Philmore crystal receiver...
which has separate binding posts for headphones.
All radios in the '20s had separate binding posts for headphones...
and all headphones had separate wires, usually with soldered-on tips to avoid fraying....
But the cable itself was always a twisted pair in one insulator, so a single plug would always have made more sense. The single plug was always available...
and it had an obvious name: phone plug.
Modern radios and audio equipment have coaxial phone plugs, which started out at the same size as Bell Tel switchboard plugs and gradually got smaller.
This 1969 catalog page shows the range of sizes, unchanged since then...
When did the standard change from separate to coax? It was certainly before the '60s. All the equipment sold and used during my lifetime had coaxial phone plugs.
GenRad, the calibration company, calibrates the answer.
A 1920 audibility meter, with separate binding posts for phones:
A 1945 wavemeter, with only a coaxial phone plug:
And the answer is: A 1939 wavemeter indicates the transition graphically! Both types of output available!
Labels: Asked and answered