The telemetry module is the topmost tool in the stack. Its main function is to collect and combine digital data from all other tools and to transmit this in a digital form via the logging wireline to the surface acquisition system. It also provides control functions and tool power to the other logging tools.

All tools in the stack communicate with the telemetry module over a common internal RS485 data bus. The telemetry module organises this data and transmits it to the surface in a single digital packet containing up to 32 x 4byte channels. Data is acquired on a depth basis with a sample interval that can be selected to optimise measurement resolution and/or logging speed. Data transmission rates (baud rates) can also be changed to maximise transmission rates on a particular wireline.

The wireline telemetry requires a minimum of 4-conductors. Industry-standard 5/16” 7-core cable offers a good compromise between electrical characteristics and mechanical strength.