Nortel i2002 (NTDU91) - can't see what I'm dialing


I’ve a couple of Nortel NTDU91 phones set up with Asterisk, and they work pretty well. However, when I pick up the headphone and start dialing a number, the screen doesn’t display the dialed digits. I know this is kinda off-topic so if questions like this are frowned upon I apologize in advance; I hoped someone here might have experience with these phones and Asterisk, and, franky, I’m not sure where else to ask.

So, can I make these phones display the dialed numbers, or make Asterisk somehow echo them back to the phone display as I’m dialing?

Thanks in advance.