New to Asterisk

just trying to find out if there is support for push-to-talk functionality on Cisco 7920s or Spectralink i640s. I know Cisco released a push-to-talk function on their recent callmanager v4.1, but haven’t found anything for asterisk yet.

I know spectralink i640s have a native push-to-talk, but haven’t seen anything regarding spectralink i640s working with Asterisk.

Any ideas?