Urmet Payphone from Tunisia blue Taxiphone from the 80s

[TeleDK]

Dear international collectors,
I have a blue wall coin telephone from Tunisia, it was produced by Urmet in Italy / Turin.
Unfortunately, I got this device defective and have gradually repaired the electronic circuitry. Now I have reached the end of my repair and the device shows an error, which is indicated with "H.S." in the display after lifting the handset. No coins are accepted, in the service menu, called up via the internal button, an error "64" is also displayed.
Can anyone help me further? Or does anyone have documentation for this device? The model is called UI 86/TU.
Many thanks for your support. 

TeleDK

[5415551212]

Thanks a interesting phone, do you have any schematics for it?

[TeleDK]

As you see...

Sorry, I looking for that.