"Don't you know a man's not dead while his name is still spoken?"

An illustrated excerpt from the novel Going Postal by Sir Terry Pratchett. It concerns immortality as it relates to a fictional communications network called The Clacks. It is a series of tall towers that relay messages through the use of shutters, lamps, and underpaid staff with keen eyes. The system has about speed of semaphore and the sophistication of dial-up internet.

Some technical details have been added by me in order to make the illustrations feel more complete.

|------------------------------|------------------------------|181-PO-002:PRELIM-TEST-MESSAGE| |------------------------------|181-PO-002:PRELIM-TEST-MESSAGE|------------------------------| |181-PO-002:PRELIM-TEST-MESSAGE|------------------------------|------------------------------|
|--------------------------------------------|--------------------------------------------|002-PEO-181:PRELIM-TX-RCVD.CONFRM-CCT-TST-3A| |--------------------------------------------|002-PEO-181:PRELIM-TX-RCVD.CONFRM-CCT-TST-3A|--------------------------------------------| |002-PEO-181:PRELIM-TX-RCVD.CONFRM-CCT-TST-3A|--------------------------------------------|--------------------------------------------|

But most of The Clacks was what was called Overhead. It contained orders from the office. Messages about messages. Chatter between towers - although this was strictly forbidden nowadays.

M-V-L: "And dead men's names?"

W-H: "Yeah, them too."

CComrc class Standard commercial Msg.
IUrgnt class Priority Msg.
PPrmOH class Primary Overhead Msg. Flow codes will switch.
GAuxOH class Overhead. Manual Flow control.
DDebug class Diagnostic Overhead. Used for automated tower / terminus returns.
SSafe mod Msg will not be evaled for Tower commands.
QChain mod Tower commands will be executed even if this is not the recieving tower.
NNoLog mod Msg will not be logged on Tower's Drum.
OOrLog mod Msg will only be logged on Originator and Reciever tower Drums.
UUTurn flow Msg is to be sent back the way it came when it reaches a terminus.
EEcho flow Msg is to be sent back once it reaches the recieving tower. This will change to S once it does so.
MMarch flow Msg is to be sent to the nearest terminus even after it reaches the recieving tower.
BBrnch flow Msg is to be sent all possible directions except originator direction if this tower is a junction.