The BSTA138 is a alarm relay suitable for standard process signals and common sensor types. The alarm directly accepts DC voltage or current input signals (0.1V up to 2kV, 0.1mA up to 2A) while low-level sensor or AC input signals require a factory fitted input-conditioning card. Special requirements for input response time can be accommodated by using the customised response option. The trip circuit is operated from the preconditioned input circuit. The trip-point is adjusted by the 15-turn trim potentiometer from the front of the module. Trip status is indicated by a red LED. The action of trip operation, e.g. high or low alarm is internally selectable by a coding plug. The standard output configuration provides a changeover contact output rated at 8A/250Vac. An optional second 8A/250Vac contact is available as change over for all 2-wire inputs and normally open for 3-wire inputs. Dead band is adjustable from 0.5 to 30% via a front accessible trim pot. Various power supply choices are available ranging from 240Vac down to 8Vdc, all contain a dual output for power isolation. Surge protection for power supply and input is standard with all BASI modules.