What is this part (photo included) Heimann LHI 1148

Can anyone identify this part? 4 leads on the bottom.
Heimann LHI 1148

Hi,
the url is indicated below below

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LHI1148

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The LHi 1148 pyroelectric infrared detector is designed for high end PIR alarm applications. It includes a Quad type pyroelectric ceramic with 4 sensitive elements connected to two FET source follower circuits. Thus it provides for dual channel output . One channel is inverse to the other. The LHi 1148 detector is available in TO-5 housing with standard infrared filter. It offers excellent common mode performance (match) and low noise.


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