Hi - i have the cb11 a while but I'm now putting int he photocells, I have 1 set and when i connect the three leds on the board are flashing, do i need to connect a second set

You don't have to connect a second set, i always connect my one pair of photocells to open/close 23+ and common 24 - on the CB11 control panel.

But the more photocells you use on your installation the safer it it is!

if all three leds are still flashing red you probably haven't done this procedure correctly

Programming of failsafe photocells model 771E/770E

1.Before the Initial Setup
2.When connecting or removing photocell(s)
- Switch off control board ( disconnect from current)
- Slip jumper on designated pins
- Dipswitch 5 to “ON”
- Connect photocell(s) according illustration
- Reconnect control board, wait short-time
- Pull jumper, wait short-time
Done! (The number of photocells connected are stored)

hope that helps.