The letter alaph takes various forms in the Syriac Serto script depending on its position in a word as do many other letters.
Alaph takes three different forms, initial unconnected, middle or final unconnected and connected.
You can see the various forms in the image below.
The letter doesn't represent a particular sound by itself. It is used before vowels that can be denoted with diacritics.
These diacritics can be written above or below the letter.
In the image above we also got the alaph zqofo which is read as 'a' and the alaph rboso which is read as 'e' pronounced as [ε],in IPA.