Programmed 4 channels of isdn 2 on bcm 50 with ddi numbers lines set to auto work fine each extn with ddi has 1 appearance and appear and ring reception teles main number programmed as ddi 2 appearances on two t7316 sets both set to ring and appear for ddi line calls come in on first channel all ok second call comes in no ring tone indicator shows call present but unhable to conect change lines to manual working all ok any ideas