Position locator for TV monitor of X-ray system - detects position of contact pin on resistance layer and inputs position data via switch in to data acquisition device

The position locator measures the resistance of the resistance layer to the contact pin and uses it as a measure of the pin's position. The contact pin (2) cooperates with a switch (5) that operates when the pin is pressed down on the resistance layer (1). The switch is connected to the data acquisition device (7) to pass an acquisition command. The contact pin can slide longitudinally in its holder and in so doing operates the switch. The switch is a contactless proximity switch. The advantage lies in avoiding chatter and the interference it causes - i.e. avoids the same point being acquired twice as the pin moves across the layer. The locator can be used with X-ray equipment with television monitor to mark out wanted areas.