Editing PDP-11/20 Power Supply Service (section)

== Outputs and protection ==
{| class="wikitable styled-table" style="width:100%; text-align:center;"
|+ '''H720 output specification (PDP-11/20 System Manual Table 2-7; H720 data sheet)'''
! Output !! Rating !! Protection
|-
| +5 V regulated || ±5%; 16 A (A, B), 22 A (E, F) || Current limit 18–22 A, about 30 A into a short (A, B); crowbar limits the output to 6.3 V
|-
| −15 V regulated || ±3%, 10 A || Current limit 12–16 A, 25 A into a short; output limited to the unregulated −22 V
|-
| −22 V unregulated || ±20%, 1 A || –
|-
| +8 V || Full-wave rectified, unfiltered, 1.5 A || Console lamps
|-
| LTC || Line-frequency sine wave clipped at ground and +5 V || For the KW11-L line clock
|-
| AC LO, DC LO || Power-fail signals, wired together across every H720 on the Unibus || On power-down DC LO follows AC LO by 7 ms
|}
<ref name="sm" /><ref name="ds" />
The descriptive text of the H720 manual gives the unregulated outputs as +8 V at 1.5 A and −25 V at 1.5 A, against −22 V at 1 A in its own data sheet and in the system manual; measure the unregulated negative rail against the higher tolerance.<ref name="h21" /><ref name="ds" /> With a basic 11/20 installed (KA11, KY11-A, MM11-E and KL11), 3.4 A at +5 V, 1.7 A at −15 V and 0.8 A of the unregulated supply are left for options.<ref name="sm" />