What was the name of the long and short pulses used by the telegraph machine

Officially, the short and long pulses are called "dits" and "dahs", but we like to call them "dots" and "dashes" anyway. Samuel Morse and Alfred Vail also developed a telegraph machine, which is what is used to send Morse Code messages.

Explanation:

offline recommendation systems option b

because recommendation systems produce a list of two ways

1. through collaborative filtering

or

2. through content-based filtering