[1] The introduction of Alphabet Google's Android 9 Pie made call recording prohibitively difficult without rooting the phone.
[2] Hardware recording devices are cumbersome and expensive, limiting their use to law enforcement agencies.
Software-based recording solutions emerged shortly after soundboards were introduced for the personal computer in the late 1980s and on mobile telephones after the release of the first smartphones.
In commercial environments VoIP was first used behind corporate PBXes in order to deploy telephones capable of delivering additional computing services.
Telcos deployed IP-based backbones later in order to more efficiently carry long-distance traffic.
[3] The rapid growth of VoIP-based telephony led to the introduction of a plethora of VoIP recording solutions.
Some services, in particular those supporting VoIP clients, appear to make a direct connection to the destination telephone.