Weak signal from Arlec entry security to siren driving a SSR instead, correction of schematic

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Joined Oct 31, 2014

This Arlec security system sends a weak 7mA at 9V or 63mW signal to a siren when the IR beam gets broken by a person or car. The voltage at the sender is 10.4V, but after 30m of cable it is 9V most likely.

The SSR requires a trigger of 7.5mA at 12V or 90mW, so if I want to drive that SSR I have to amplify the signal to switch lights, etc. on. The enclosed sketch suggests a 3.3V output from an Arduino board, so it will not match the 9V output of the Arlec. The relay is an SSR and does not have a coil, so the diode (?) may not be required - help!

Being more of a software man, I am ignorant if the figures for the 10k resistor and the suggestion of the 2N2222 transistor is correct for a 9V input signal for the low-side driver are correct - help!