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Just apply Euler’s formula. Hence $$|e^{at + jbt}|^2 = |e^{at} e^{jbt}|^2 = |e^{at} [\cos(bt) + j \sin(b t)]|^2.$$ Thus $$|e^{at + jbt}|^2 = e^{2at} [\cos^2(b t) + \sin^2(b t)] = e^{2at}.$$


I need to figure out the communication bus type used in it. As commented, those ICs are only used for RS-232 (they cannot be used for RS-422 or RS-485). Your CPU card might have other interfaces too, of course, but RS-232 is the answer about what interface type those ICs are used for. Here is an example - an old IBM PC-compatible serial card, showing ...


In this context, it indicates that the TxD and RxD signals are transmitted differentially. There is TxD+ and a TxD- line, and it is the relative voltage between them that indicates a logical high or low signal. This differential signalling is used to improve noise immunity, and is common with relatively low speed signals that must endure potentially harsh ...


The +/- means that the transmitted and received signals are 'bipolar' relative to ground. 1 / idle / spacing / logical 1 is usually negative relative to ground. 0 / active / logical 0 is usually positive relative to ground. Where a polarity is not specified (eg RS422) all signal levels are always positive relative to ground - but in a balanced signalling ...


Try register 515 instead of 40515. the 4x prefix is just to say "holding registers" If that doesn't work, try 514, for register addresses vs register numbers. The "comm light" can blink just because it received a modbus request it understood, but had no answer for. It's nice if devices reply with "illegal register" and it's in the protocol docs, but you ...


I assume, that "reading" the signal works simplified very similar to sending it. I would try and decouple the two rails with a capacitor/highpass and amplify the noise (of which hopefully a good portion is the signal). Just make sure you filter all the frequencies you don't want.

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