The A520 has 3 Phono connectors.
Your interested in.
Back RF (60Hz NTSC in your Case)
Here you got "RF" to your "RF" input on your TV
Side Composite
Composite Video - Composite Video to either a Scart or Phono / BNC connectors on your TV
Audio In - Y single to dual phono lead to the back of the A500
The A500 also has a mono video output as the last connector on the back.
Have you got a NTSC 500 but a PAL or SECAM modulator ?