Spare part no. R311850. Power supply, 100-240VAC, for 501-7, 501-17, 501-19, 501-23, 501-25, 501-27, 501-29 and 501-49. To be used when the power indication diode does not light up when plugged in. The power supply is easily changed and is found either in a fitting under the table top or in the cable tray. No use of tools nessecary. Available as shown in the picture.