10.49.3. User Interface 
- The user may either depress a key (SPKRCALL) or dial an access
code (SPKRCALL), followed by dialing a destination extension number,
to initiate a "Speaker Call - One-Way" call. A one-way connection
shall immediately be established between the user and the dialed destination,
if the following criteria are met:
- The destination is not busy, not off-hook, not in hands-free operation,
and is not in program mode.
- The destination is not marked for voice call protection.
- The station is not restricted from terminating to that destination
(e.g. ITR Internal Traffic Restriction).
- An external dial tone shall alert the originator that the one-way connection
has been established, and that the one-way call can begin.
- The one-way connection shall be converted to a single two-way connection
upon the destination's going off hook, via the handset only.
- A "Speaker Call - One way" call can be initiated by an
analog or digital telephone.
- When the destination party presses the speaker key, the call will
be disconnected.
- When the destination party presses a line key (either the one on
which the call is pending, or any other line key), the call will be disconnected.