D-Link DCS-5615 User Manual page 52

Configuration
DI
Network camera provides a general I/O terminal block with one digital input
for device control. The I/O connector provides the physical interface for digital
input (DI+. GND) that is used for connecting a diversity of external alarm
devices to the camera such as IR-Sensors. Once triggered images will be
taken and e-mailed.
DI Schematics
D-Link DCS-5615 User Manual 52