When I first read this, I thought sure he was talking about the MDC-1200 identifier 'squawk' that can be enabled either before, after, or before and after a transmission. I did some looking around today, and this is what I have come up with:
I do not have a codeplug in front of me, and I have not enabled this option in a few years. However, going through the help file, it apperas that you need to enable MDC in the Signaling Configuration window by checking the appropriate checkbox, and then go to the Basic tab of the MDC System window, set the PTT ID Type to Pre & Post.
While in the Basic tab of the MDC System window, you should probably also set the Primary ID to an appropriate value between 0x0001 and 0xDEEE and set the Group ID to an appropriate value between 0x0 and 0xEEE. While in the Basic tab of the MDC System window, you should probably also enable the Display Decode ID option so that your HD1250 will display the Primary ID on its screen when any other radio on that frequency transmits its Primary ID.
After the Display Decode ID function is enabled, you could even enable Reverse Aliasing and create a Call List including aliases for other radios by Primary ID. This would allow you to display a custom alias on the screen of your HT1250 for each MDC enabled radio in the Call List.
Good luck!