Jun 20
What does “Unable to accept (or answer) call in current state” mean?
What do the error messages “Unable to accept call in the current state” and “Unable to answer call in the current state” mean?
There are three computers involved: The PSTN-side switch (i.e., the telephone company), the CPU on the Dialogic ISDN board inside the Teleplex server, and the CPU running Teleplex.
A simplified typical inbound call flow is shown below.
| PSTN | ISDN Board | Teleplex |
| (1) Set ISDN Setup message (“here is a new call”) | ||
| (2) Catch the Setup message, send to the application. | ||
| (3) Catch the Setup message. | ||
| (4) If we want to handle the call, send Accept message, otherwise reject it with a Disconnect message. | ||
| (5) Catch Accept message, send to PSTN. | ||
| (6) Catch Accept message. | ||
| (7) Send Answer message. | ||
| (8) Catch Answer message, send to PSTN. | ||
|
(9) Connect calls. |
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The tricky part, and the source of the error occurs in the middle column. Suppose, for example, that the caller hangs up sometime during steps (3) or (4). (This really means, because everything is so fast, that the caller dialed the number and immediately hung up-even before the first ring.) The board knows that the caller wants to disconnect, and may have even informed the Dialogic driver. However, Teleplex is still waiting, in parallel, for the Accept function to return. So when the Accept message arrives at the board from the application in Step (5), the board says “No silly!! Unable to accept call in the current state”. (Sorry. How was I to know?)
On the Teleplex-side, the function to Accept the call returns an error code, and Teleplex displays an error message.
You can ignore these “error” messages, which are not really errors at all.
Finally, we changed Teleplex from Version 3.51.0.8 so it will display an informational rather than an error for this case.