[Asterisk-Users] Message waiting indicators

[Oliver Wilcock]

A post in 2002 refered to Mike Sandman as a source for inexpensive (cheap) 
message waiting indicators.  I called Mike but he doesn't know what 
Asterisk is (!) and wants to know what type of phone system I have or what 
protocol it uses so that he can send me a compatible indicator.  I tried 
these acronyms on him: ADSI, MDMF, SDMF but he doesn't recognize them. 
What can I tell him so that I can order the right part?  Or which popular 
switch is Asterisk compatible with?

The post to which I refer:
http://www.marko.net/asterisk/archives/0209/0588.html

The style I'm interested in: Modular #WAL2D