When using a 'panic dial' mode in the Telos Zephyr XStream, most noticeably with the 10baseT version, occasionally - if the 'panic dial' mode is asserted and quickly dropped - even though the first line is dropped, the XStream will keep trying to connect the second ISDN line, and that line will stay connected until someone or something intervenes. It's only happened a few times, but it can result in some expensive ISDN bills if it does.
Take no chances! Look over this HOT TIP from the Zephyr XStream user manual and implement the recommended 'safety net' suggestions.
Users have found the following 'Panic Dial Tricks' handy:
1. Mode reset. Create the Dial Setup(s) to be used without any phone numbers and to "include" codec information. Name them after the associated modes stored with the setup(s). You can now use push a momentary switch connected to the panic dial input(s) and XStream will switch to a designated mode ready for an incoming call.
2. Drop and reset. Same as above. Since Panic Dial takes precedence over standard calls, you can push this momentary switch and drop a call and return to a default configuration (as programmed into the associated setup) ready for an incoming call. Some users have done this with an external timer that automatically closes the contacts a few times a day. While the potential drawbacks are obvious, this can prevent 48 hour phone calls over the weekend!
3. Quick dialer. Connect a push button interlocking switch assembly (9 by 1 pole, single throw, interlocked such that only one can be pressed at a time). Leave one unconnected and connect the other 8 to the 8 logic inputs. Configure the inputs for Panic Dial. You can now call any of the first eight Dial Setups by pressing the appropriate button. Pushing the unconnected button would drop the call. When used in conjunction with an LED connected to an output, makes this a slick (but limited) remote control interface.
Alternatively, you can use an 8-pole rotary switch to select a line, and a simple toggle switch to connect or disconnect the call.