What are these symbols (letter inside square) standing for?

[rsko]

I found this digital delay schematic on generalguitargadgets but I have no ideea what those 3 symbols marked A, P, and R inside a square mean. I'm new to electronics, can anyone help me?
**broken link removed**

 

[IanP]

These symbols are used to make the schematic less complicated. All you have to do is to connect A with the other As, P with other Ps and R with other Rs.

BTW. P represents here voltage generated by the 12V voltage regulator, so its voltage value is +12V.
R is a voltage value generated by 1k---1k voltage divider and its voltage value is +6V.
A, on the other hand, is just a signal at the output of 1/2TL072

:wink:
IanP