Payphone 500 / 600 handsets
I have some BT handsets with the armoured cord as used on Payphone 500 / 600 (the 700 style handsets, not the flat angular ones)
They are of course riveted shut preventing internal examination. They have 6 wire cords (red, grn, blu, whi, org, blk)
Are these standard 700 style inserts and on the standard colours red+grn for receiver, blue+white for xmtr? as I am having difficulties getting them working.
On one of them red+grn makes the mouthpiece work as a receiver.
I want to repurpose them for the Pratical Wireless 741 op-amp intercom requiring 700 type circuitry.
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