Sometimes a method is supplied with a digital private branch exchange (PBX) that can process the proprietary signal (usually a conversion box) before being channeled to a computer for recording.
Alternatively a hardware adapter can be used on a telephone handset as the digital signal is converted at that point to analogue.
There are also solutions which use packet capture technology to passively record VoIP phone calls on the LAN.
Direct recording of mobile phone calls requires a hardware adapter connected to the handset.
However, such systems are typically expensive to purchase and change the way that calls are made, incurring running costs.