Commands are:

a	 answer incoming call.
c str	 dial str after parsing.
c/n str	 dial str on call appearance n.
C str	 dial str, literally.
d	 drop.
h	 hold.
k str	 conference call to str.
k	 complete conference call.
r id	 reconnect call on hold (first one if id missing).
q name	 query local directory.
s	 show the status of calls.
t name	 run `tel'(1) on name.
T	 set clock (API phones only).
x str	 transfer active call to str.
x	 complete call transfer.
!str	 run str as a (non-interactive) shell command.
[0-9]... send touchtones if call is active, else dial.
[#*]...
. str	 send str as touchtones.
?	 print this message.