Option D - Big Foot Sensor and Muti-Sensor.
The Big Foot sensor also known as the Ground Microphone, is to be used on hard surfaces, concrete, asphalt, tile, etc. A flexible rubber shield helps pre-vent outside sounds from interfering with the sounds from the buried pipe. Press and hold the red button near the handle to mute the audio from the probe and suppress loud sounds when the probe is moved.
The Muti-Sensor is used for both the ground microphone and direct contact applications

What's in the Box:

• (1) Heavy-Duty Carrying Case
• (1) Probe Cable Assembly
• (1) Operation Manual
• (1) Control Unit
• (1) Head Phones
• (1) Multi-Sensor
• (1) Carry Strap
• (1) Housing Bracket
• (1) Sounds Rods
• (1) Big Foot

Specifications:

• Operating Frequency:  60 Hz – 6 kHz, Gain = 95 db; 20 Hz – 60 Hz, Gain > 90 dB
• Filter Types and Frequency Ranges:  All Pass: 60 Hz to 6 kHz; Low Pass: Adjustable cut-off frequency from 150 Hz to 2.4 kHz; High Pass: Adjustable pass band frequency from 150 Hz to 2.4 kHz; Band Pass: Adjustable center frequency from 150 Hz to 2.4 kHz; Notch Filter: Adjustable center frequency rejection from 150 Hz to 2.4 kHz. Can be used simultaneously with any filter option
• Output Indications:  Audio: High performance headphones (64 ohms)
• Visual: LCD bargraph and 2-digit numeric display
• Grade of Protection: Splash Proof
• Battery Test:  Automatic, real time battery level indicator
• Battery Quantity/Type:  Two, 9 Volt alkaline
• Battery Life:  50 Hours (approximate)
• Carrying Case Dimensions:  21”x 6”x 14”
• Weight:  10 lbs