(57) 0 A borehole logging system employs a transmitter of acoustic energy pulses and at least one receiver for producing an analog signal representative of the acoustic pulses traveling from the transmitter to the receiver through the formation adjacent the borehole as the logging system is moved through the borehole. A sample-and-hold unit 21 samples the analog signal and an analog-to-digital converter 23 produces a digital word representative of the sampled analog signal. A plurality of digital data words are stored in a memory 24 and converted to a digital serial word for transmission to the surface of the earth over the logging cable 26.