TOSHIBA Photocoupler IRED & Photo-Transistor TLP570, TLP571 TLP570,TLP571 Programmable Controllers AC / DC-Input Module Solid State Relay Unit: mm The TOSHIBA TLP570 and TLP571 consist of a Darlington connected phototransistor optically coupled to an infrared emitting diode in a six lead plastic DIP package. TLP570 has no-base internal connection for high-EMI environments. Collector-emitter voltage: 35 V (min) Current transfer ratio: 1000 % (min) Isolation voltage: 2500 Vrm.