3 conductor cord to 4 conductor early AE80

[WEBellSystemChristian]

Does anyone have a diagram or instructions for converting a 3 conductor AE line cord into a 4 conductor handset cord on an early type 80?

I know I have to use a seperate conductor to bridge from a conductor in the cord to the receiver, but do I have to use more than one?

Which terminals do I connect the seperate conductor(s) to?

Do I have to do the same in the phone itself?

[rdelius]

with a 4 wire handset cord,the  common connsection  would be in the set   Rec yellow and black Trans green and red.   old handset had the green tied togather as a common inside the handset
So with a 4 wire cord  R=Y,t=R and C=bk,gn.