Whenever you don't know the voltage look at the ics' to see what they're rated for.. The circuit you show has a 5volt supply and a 24 volt supply..
The logic ,or control is 5v and the motor is 24..
You will need both to make this operate properly...
74LS04 is TTL chip expecting input signals in range 0 to 5V.
Quick look in L6506 datasheet confirms that all inputs (including pins 6 and 4) have pretty much the same rating (0-3 normal with absolute maximum rating of 7V). R1 and R2 are pull-up resistors to Vcc so Vcc should be 5V.
thanx for replying ,i'm assume that is a logic input so i will try to use 5volt as it Vcc and same with "direction" and "motor on/off"...hope this will work.....thanx again!