Observation posts, patrols and the camp stay in touch by short-range signals such as a whistle, a shielded lamp or a pull-line cord, and by a runner when the message is too long for a code. Whatever the means, every post and patrol must use one signal table, because the same whistle pattern meaning different things at different places is how a warning turns into confusion.
Part of Watch and Patrol Scheduling
Communication between posts is the set of short-range signals and messengers that let sentries, patrols and the settlement exchange alarms and information.
What Posts Need To Say
Posts need to do four things: raise an alarm quickly, acknowledge a message, report a contact in detail, and call for relief or help. The first two are signals; the last two may need a runner. All of them must work at night, in rain, and without giving the post’s position away more than necessary.
Matching The Means To The Distance
| Distance between sender and receiver | Usual means | Notes |
|---|---|---|
| Within earshot, tens of metres | Hand signals, low voice | A normal voice is audible at 100 to 200 m in still air (Noise Discipline), so use hand signals if outsiders could be close |
| Up to about 500 m | Whistle | The parent signal-systems range for whistles; a lamp or flag if line of sight exists |
| Hundreds of metres to a few km | Horn, drum, lamp, mirror, runner | See Signal Systems and Communication |
| Between two posts with a cord between them | Pull-line | Silent and hard to detect, short spans only |
Time By Foot
A runner or a walker at 5 km/h covers 1.39 m/s. A post 500 m from the camp is 500 / 1.39 = 360 seconds, 6 minutes away on foot; a post 1 km away is 12 minutes. The warning time at the other end is whatever remains after the runner arrives. Signals reach in seconds, which is why alarms go by signal and detail goes by runner (Runner Systems).
Three Rules For Any Post Network
- One table. The parent watch article gives posts one long blast for attention, two short for acknowledged and three rapid for emergency, and gives patrols one blast for stop, two for come to me and three for danger. Two blasts means “acknowledged” at one end and “come to me” at another. Use the single table in Simple Code Tables, with the whistle set at the end of it.
- Every message is acknowledged. A signal not answered is assumed unheard.
- No post is left empty to deliver a message. A sentry on a one-person post cannot run a message without leaving the post; the message goes by signal, or the runner comes from the camp, or the post is a pair.
Method: Setting Up The Network
Step 1: List every pair of post, patrol route and camp that must communicate.
Step 2: Choose the lowest-exposure means for each pair that still works at night and in poor weather.
Step 3: Print one signal table and put it in every post, with the day’s password and the lamp and whistle codes.
Step 4: Test every link at night, at the real distances, and with the wind as it is on a bad night.
Step 5: Drill the failure. Switch off one link and see how the others cope.
Common Mistakes
- Choosing the means by convenience. A lamp is easy and shows the post; a pull-line is silent but breaks.
- Different codes at each post. Confusion in a real alarm.
- Never testing the quiet means. The pull-line that nobody has tried in a gale fails when needed.
What’s Next
- Learn next: Visual Signals — silent sight-line signals between posts
- Combine with: Audio Signals — whistles and the cost of being heard