Abstract: A portable, battery operated personal alarm and motion detector has two passive infrared (PIR) elements for sensing motion in two corresponding and oppositely directed fields of view, with each field of view being easily and selectably variable during set-up. A rotatable turret is associated with each PIR element and has several windows such that each window is selectably alignable with the PIR element by manual rotation of the turret. Each of the windows is provided with a lens or lens cluster which, when aligned with the PIR element, defines a different field of view in which motion is detectable by that element. An integrally and pivotally attached base member provides a support by which the device can be tilted to, and maintained in, a selectable orientation for purposes of aiming. Different modes of operation are selectable, including a manually armed alarm mode in which the person carrying the device only needs to depress a panic button in order for the device to emit a high decibel alarm.