This module serves as a double balanced input on a Combo card facilitating the jack or XLR connection. C1, C2, C3 constituting an RFI filter to eliminate interference. C4 C5 blocks any DC component that would be present on the transmission line. R1 and R2 are Pull down resistors of these 2 condensers. That1240 converts the balanced signal to an unbalanced signal. R3 R4 C7 C8 filter the power supplies. A +/- 15v distribution bus has been planned to increase the number of modules. The old SSM2141 & 2143 can still be used, as can Burr Brown's INA134. Thatcorp also distributes a whole series of differential stages according to your selection criteria
.I placed 4 of these circuits at the input of a 4X4 audio matrix. The lever switches are Lift ground. See attached photo
If you do not have a lift ground, you have the leisure to manufacture a cable whose point 1 has been cut.
This module can easily be placed in front of the summing subtractor which is the subject of another project
https://www.elektormagazine.fr/labs/sum-diff-with-that1240