Sigma BM-286A service manual Theory of Operation

4. THEORY OF OPERATION page 32

4.2.7. Receiver Board, RECV-1:

Refer to "RECV-1 Schematic Diagram" Drawing15 and "RECV-1 Component Designator" Drawing 16 (Appendix F.).

The receiver board is a quad, differential line receiver. This board converts the differential inputs to +5 volt logic outputs. There is a +5 volt regulator on board. This board controls the solid state relay for power to the scale controller.

4.2.8. Transmitter Board, TRANS-1:

Refer to "TRAN-1 Schematic Diagram" Drawing13 and "TRAN-1 Component Designator" Drawing 14 (Appendix F.).

The transmitter board is a quad, differential line transmitter. This board receives +5 volt logic inputs and converts them to differential outputs. There is a +5 volt regulator on board. This board has the input from the door position sensor.

4.2.9. Low Voltage Power Supply:

Low voltage (+5 and ±12Vdc) for the system are supplied by an open frame power supply.

4.2.10. Scale Controller:

The controller is located on top of the board rack system and displays the current weight in pounds. This unit receives its power from the solid state relay controlled by the RECV-1 board and DOS computer. The NT machine sends and receives serial ASCII data from the unit via COM3.

Model BM-286A