TDL-9915 RF Receiver

I have just found this receiver and matching 4 button key fob transmitter in my 'box of bits' and want to make sure i understand the pin connections.

the 7 pins care labeled :-

VCC = Power in - red line VT = GND power out - black line D0 = Output 0 D1 = Output 1 D2 = Output 2 D3 = Output 3

there is also this picture on the Internet :-

any ideas what the VT pin is ? Could it be a 'data received' confirmation to connect an LED to ?