Use the "ATD" command to connect actively!
Besides telephone numbers, various ISDN parameters can be adjusted to select services and transfer protocols. By default, cFos is set to transmit data with X.75 as level 2 protocol and transparent (i.e., no) level 3 protocol. Parameters can be set manually by so-called 'modem registers' (please refer to modem.txt for more details).
To make choosing among the most important data transfer protocols as simple as possible, cFos allows you to set the following by AT commands:
We strongly recommend you use these AT commands for connecting. But you can also configure how a connection is established by setting different 'registers' for special applications.
Here are some examples:
We urge you to take a close look at the modem.txt file, which lists more than 100 registers that allow you to fine-tune your connections and configure special features.
For CAPI 2.0, you have to configure MSNs and subaddresses (cf. subadd.htm). This is explained in more detail under "Connecting Passively" below.
During passive connection, cFos is waiting for a call on one or several predefined MSNs or EAZs with certain service signatures (data service, telephony, etc.). You need to inform CAPI to which ISDN service signatures it should respond by setting the "CIP Mask" with registers S107/S108 (CAPI 2.0).
Service features can, for instance, be set by "ATS107=<bit pattern>."
For example, bit 2 activates incoming calls with a "data transfer" service signature, while bits 1 and 4 activate calls for "telephone service."
Both services can also be set with "AT&I...", where "A" stands for analog while "D" represents data transfer. Thus, entering "AT&IAD" would have cFos "listen" to both.
By default, cFos is set respond to "data transfer."
For more on MSN settings, refer to /cfos-professional/subadd.htm. As some phone switches will allow a connection only when calling with the correct MSN, you should always use "AT&A0=<msn>" to enter at least one MSN (without area code).
On incoming calls with a "telephony" service signature, cFos will select "bit-transparent" as B2 and "transparent" as B3 protocol. This lets you receive a data stream of 8000 cps with digitized analog samples. But keep in mind that only "data transfer" is activated as default service.
On incoming calls with a "data transfer" service signature, cFos is (due to CAPI design restrictions) limited to choosing from transfer protocols depending on what BC, LLC and HLC signaling elements are being transmitted (for CAPI 2.0). Thereafter, an automatic change of protocol is not possible. This is why in contrast to conventional modems protocols cannot be negotiated once a connection has been established. To be on the safe side, enter "ATS76=1" so that cFos will also use the protocols set for outgoing calls to accept incoming calls that transmit no signaling elements. With AT S76=2 these protocols are used, even if there are signaling elements.
Please note there are no officially accepted signaling elements for V.110, 38400 bps, asynchronous. However, cFos comes with substitute values for CAPI 2.0 that can often be used for detection and are usually transmitted by most networks. Failing that, "ATB1 S76=1" can be used to force this choice of protocol.