There are several reasons why you might want to record a telephone conversation: you could be an interviewer keeping records of your prospective employees or you might be a journalist gathering evidence for a story. Either way, you are going to need to record the conversation. Using a PC as a direct recording device is much better than a traditional tape recorder because it can manage hundreds of hours of chat at a time and also store digital, backed-up copies of your conversations.
Invest in some telephone-to-PC recording software and equipment. Companies such as ARTCOM (U.S.) and Re-Tell (U.K.) sell bundles that include recording software and equipment. For example, ARTCOM sells a PCM-2 USB package that can record up to eight telephone lines, microphones or radios. This particular ARTCOM bundle includes USB cables that can connect to digital and analogue phone outputs (see Resources). These packages usually include software that can record hundreds of hours of calls, and some can even be set up to record when the phone is picked up or used to call someone else. See the Resources section for some links to popular phone-to-PC packages.
Purchase a telephone microphone to connect directly to your PC. The most efficient model that gets the highest-quality results is an in-ear microphone. As the name suggests, an in-ear mic sits inside your ear cavity and, while the phone is pressed to that ear, the conversation transmitted through the phone speaker is recorded. The input cable plugs directly into your PC or laptop and then records through any recording software installed on your computer. If the microphone is of decent quality, it will also pick up your own speaking voice and not impair your hearing or understanding of the other speaker. These in-ear microphones are also recorded on flat frequencies, which means the other person cannot tell that you are recording the telephone conversation. You can purchase an in-ear microphone from websites such as Planet Headset and companies such as Sound Professionals (see Resources).
Record a conversation using a laptop with a built-in microphone. This is only possible if your telephone has a speakerphone option. Although this may seem a little primitive, it is a cost-effective solution in comparison to phone-to-PC bundles, which can cost in excess of £325. The basic set-up is that you open a recording program on your laptop (most modern laptops come with a built-in microphone and recording program) and set your telephone to its speaker mode. As the conversation is transmitted through the speakerphone, the laptop is recording the voices. This is good idea for an impromptu recording on the move or when you don't have all the excess equipment to hand: just turn on your laptop mic and speak away. Unfortunately, because laptop microphones record everything in their surroundings, any background voices or noises will also be recorded so ensure that you speak clearly or hold the telephone speakerphone up to the laptop.
Know the legal issues that surround telephone recordings because recording others without their consent can be illegal. Consult your state or country laws for clarity on phone recording rules and regulations.