Yes, your IR received needs to switch the pin 15 input to GND as in the first option above. The PMDX-126 inputs expect any one of the following kinds of inputs:
- Open circuit or connected to GND, usually for mechanical switches, "NPN" style or "open collector" style sensors
- Open circuit or connected to "+12U" (from the PMDX-126 board) or an external +24VDC power supply, for "PNP" style sensors
- Connected to +5V or GND, usually for sensors with "totem-pole" style outputs (also called TTL or CMOS outputs)
Bob