There was no need for guillotines on the Saturn V. Signals between stages were passed through mated electrical connectors, which simply pulled apart during stage separation. There even were pins in the connectors to sense the continuity of the connection. (Sources for this answer are the Saturn V Flight Manual.)
INTERSTAGE DATA FLOW
In order for the Saturn V launch vehicle and Apollo spacecraft to accomplish their objectives, a continuous flow of data is necessary throughout the vehicle. Data flow is in both directions: from spacecraft to stages, and from stages to the spacecraft. The IU serves as a central data processor, and nearly all data flows through the IU.
Specific data has been categorized and tabulated to reflect, in figure 1-4, the type of data generated, its source and its flow. Each stage interface also includes a confidence loop, wired in series through interstage electrical connectors, which assures the Launch Vehicle Digital Computer (LVDC) in the IU that these connectors are mated satisfactorily.
Each stage had its own batteries for power, and no fluids were passed between stages. Thus, explosive charges only needed to separate the structures of the stages; there was no need for guillotines.
The digital signals from the Launch Vehicle Digital Computer were routed to boxes on each stage, near its associated pyrotechnic, called "EBW (explosive bridgewire) firing units". These units generated electrical pulses with enough energy to detonate the explosive:
The storage capacitor in each of the EBW firing units is charged by 28 vdc power during the latter part of S-IC boost. The trigger signal causes the storage capacitor to discharge into an EBW detonator which explodes the bridgewire to release energy to detonate the explosive charge in the detonator.
The EBW firing units are armed by charging their storage capacitors to 2300 volts about five seconds after the S-IVB ullage rockets have stopped firing. A trigger signal releases the high voltage pulse to explode the bridgewire in the EBW detonator. Either detonator will detonate both CDF assemblies (figure 6-26) through the detonator block.
The ordnance systems on the Saturn V are as follows, in the order that they are ignited:
- 8 retrorockets on the S-IC, ignited by a redundant pair of EBW firing units, to pull the first stage away from the rest of the rocket during separation.
- A redundant pair of EBW firing units on the interstage ring, which detonate a linear-shaped charge to separate the S-IC first stage from the interstage ring.
- 4 ullage rockets on the S-II second stage, ignited by a redundant pair of EBW firing units, to settle the propellants in their tanks and to help with the separation of the interstage ring.
- Another redundant pair of EBW firing units on the interstage ring, which detonate a linear-shaped charge to separate the interstage ring from the S-II second stage. Note that this separation disconnects the signal that caused it (although it does not matter).
- 4 retrorockets on the S-II, ignited by a redundant pair of EBW firing units, to pull the second stage away from the rest of the rocket during separation.
- A redundant pair of EBW firing units on the interstage attached atop the second stage, which servers the tension straps between the S-II and S-IVB stages. This is another separation that disconnects the signal that causes it.
- Two ullage rockets on the S-IVB third stage, ignited by a redundant pair of EBW units.
- A redundant pair of EBW on the S-IVB to detonate four frangible nuts, to jettison the ullage motor assembly to save weight.
In addition, each stage has a redundant pair of self-destruct systems. These are controlled by a radio signal from the range safety officer, rather than the Launch Vehicle Digital Computer.