Introduction

VDR is a safety device used in exchanges for protection of exchange cards. Failure  of VDR Cards may damage exchange circuitry resulting in extreme economic losses.  With our VDR test board we can check all VDRs, without removing them from their PCB. The VDR module is attached to the connector fixed on the unit. Unit is switched on. Particular VDR is selected through a set of  switches. Then for that selected VDR  ‘Low’ button is pressed. In this case low voltage of high frequency is applied to VDR through some circuit. For good VDR buzzer will not start. For short VDR buzzer will start.  Next press ‘High’ button. Now high voltage of high frequency is applied. For good VDR, buzzer will start. But for open VDR buzzer will not start. Similarly we can check other VDRs in that module.