oil pressure sending unit

[mail.beol.net]

Subject car is '90 100, ( but my '90 200 looks the same).
I get a oil pressure warning symbol on the dash display.  Oil pressure guage reads ok and I temporarily installed a mechanical guage and pressure is OK.
The Bentley shows two oil pressure switches besides the oil pressure sending unit.  I can only find the white, high pressure switch on either car. Not the brown low pressure switch.
Could the second terminal on the oil pressure sending unit be the low switch?  TIA for any help.
Nick