ISDNphone enables computer-telephony by allowing phone calls to be made from a PC through an ISDN-adapter, with speech processing capabilities.

If you're looking for professional-quality sound, then you'll want to use DSP Mode with one of the supported adapters, including Eicon Networks DIVA ISDN+CT, Billion Electrics BIPAC PCIpro, or Telekom T-Concept PC & T-View 100 PC. Note that support for DSP-ISDN-adapters is only available in DSP Mode, which can be dynamically switched in the application.
One of the standout features of ISDNphone is its user interface: it's easy to use and can be managed by a mouse or keyboard. You can make phone calls using the built-in phonebook with speed dial, or from other applications with TAPI or command-line access. And if you need to record voice data, ISDNphone can take care of that too, storing it on disk for future reference.
As for call management, ISDNphone includes a call journal feature that provides detailed information on all incoming and outgoing calls, so you can track your usage and monitor your call activity. You'll also find powerful integration of ISDN features like call forwarding and call deflection, which allow you to redirect callers to different numbers if needed.
Pricing for ISDNphone is affordable too, with options for both Standard Mode (25 EUR) and DSP Mode (60 EUR). So if you're on the hunt for a versatile, feature-rich ISDN phone software, ISDNphone might be worth checking out.
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