Tower Microphone TM20 for BATmode systems

£633.90 Ex. VAT
Order to reserve stock (Backorder)

Electret Ultrasonic Microphone with Test Signal Speaker

The electret ultrasonic tower microphone TM20 was specially designed for mounting in the tower wall of large wind turbines for the qualitative detection of bat activity at the level of the lower rotor tips. While the focus of the tower microphone TM10 was on having the smallest possible diameter, the TM20 includes a 40kHz test signal speaker in addition to the microphone. As for the microphone discs for nacelles, this speaker is used to play a daily 40kHz test tone for checking and logging the microphone sensitivity during a continuous long-term monitoring. With a microphone diameter of only 20mm, the required diameter of the mounting hole of 22mm is still extremely small. For mounting in the tower wall, the optional TM20 - Mounting-Kit is available. The tripod of the Mounting-Kit slides along a rod, which is fixed to the microphone. Thus, the microphone can be easily fixed in tower walls with different wall thicknesses up to 450mm and allows a defined positioning of the microphone tip. The tripod is mounted on the tower inner wall using either magnetic feet, adhesive pads or screws (see the Drilling Plan - TM20 in Product Attachment). To prevent the ingress of rainwater through the mounting hole it can be drilled slightly sloping into the tower wall. To further increase the reliability of the microphone in adverse weather conditions, the TM20 integrates a microphone heater, which reduces condensation on the microphone. Due to the M3 mounting bolt on the back of the microphone, the microphone is also ideal for alternative measuring situations, such as on measuring masts, in addition to the use in the tower of wind turbines. Like all other microphones, the TM20 is compatible with BATmode 2S and BATmode 2S+ as well as the UltraSoundGate 116Hnbm and 416Hnbm from Avisoft Bioacoustics.

Note : To reduce electromagnetic interferences, we recommend to place the BATbox with the detection system as close as possible to the microphone hole and as far away as possible from interference sources such as power and control cables. For this the microphone is delivered with a 3m connection cable. In principle, it is also possible to install the BATbox on the tower base and to use an extended microphone cable. However, this may cause a significant reduction in recording quality.

Main features

  • Knowles FG - Microphone capsule
  • 40kHz test signal speaker
  • Integrated microphone heating
  • ∅ 20mm / Length 55mm
  • M3 mounting bolt
  • Tower wall mounting with TM20 - Mounting Kit available separately


  • Knowles FG - Microphone capsule
  • 40kHz test signal speaker
  • Microphone heating
  • Approximate input-referred self-noise level (bandwidth: 30-50 kHz): 26 dB SPL
  • Approximate sensitivity: 500mV / Pa
  • Power supply: 5V / 25mA provided by UltraSoundGate xx16Hnbm
  • Connector: male XLR-5 plug
  • ∅ 20mm / Length 55mm
  • Required bore hole ∅: 22mm
  • M3 mounting bolt
  • Cable length: 3m
  • Tripod TM20-Mounting Kit optionally available for tower wall mounting

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Important Information About Backorders

At Wildcare there are times when items are only available on a backorder basis, either due to high demand or if the item is a special order item. We refer to these as ‘backorder items.

Backorder items are clearly listed on our website as ‘Order To Reserve Stock (Backorder)’. Items that are in stock and ready to be shipped immediately are listed as ‘In Stock’.

When you place an order for a back order item or an order that includes back order items, a member of our team will be in contact within 48 hours of your order to confirm the lead time for delivery. For any queries before then, please call us on: 01451 833 181

Avoiding Disappointment

We cannot guarantee that a backordered item will come back into stock or be delivered for a specific date, however we will always do our best to keep you informed and updated.

If your back order is urgent or required within a specific time frame we suggest to call us on 01451 833 181 so we can keep your requirements in mind throughout the waiting period.


If you receive damaged items or the wrong goods, please let us know straight away so that we can arrange for them to be returned to us and replaced as quickly as possible.

You will need to obtain a Returns Number  - please call us on 01451 833 181 or email

Please return goods, WITH THE RETURNS NUMBER MARKED ON THE PARCEL to: Wildcare, Eastgate House, Moreton Road, Longborough, GL56 0QJ

We may ask for a photograph any damaged items before we agree to replace them.

Please click here to view our full returns policy.