The service, appropriately named `LiarCard,' requires users to route a phone call via a US toll-free number, with onward dialling to the required party whose voice is to be analysed for truthfulness and other stress issues.

The LiarCard service is billed as detecting the emotional content in speech patterns, which provides information about the speaker's mental and emotional state during the call.

TelTech is promoting the service as a way to get an edge in a business negotiation, or to find better employees or suppliers.

According to the company, LiarCard ‘listens’ to the millisecond changes that occur in the human voice when a thought process starts in the brain and extrapolates data based on the vocal changes.

The service - which is currently in beta test - costs $10 for 30 minutes, with other subscription models available and requires users to call LiarCard's US toll-free number, input their PIN and the destination phone number.

The facility then provides an audio ‘heartbeat pulse’ to the subscriber, with the pulse beating faster when the called party is stressed, and slowing down when they become less stressed, and, presumably, when they are telling the truth.

A buzz is also played in the background when the called party is suspected of not telling the truth or is in an extreme state of mind.

The service also provides a Web-based dashboard interface that provides visual graphics, such as a `truth indicator, as the called party speaks.

Infosecurity notes that using the LiarCard service from the UK may contravene several UK laws, notably the Regulation of Investigatory Powers Act 2000; the Telecommunications (Lawful Business Practice) (Interception of Communications) Regulations 2000; and the Telecommunications (Data Protection and Privacy) Regulations 1999.