I'll let you wonder how that was done for a while. Card 16 is just fantastic, it is the police telephone pillar. To meet the particular requirements of police communication the Post Office has developed a special telephone system. This includes street pillars, the cast iron heads of which as fitted with two doors. The police hold keys of one door, behind which is a telephone giving access via the local police switchboard to the main telephone system.
Conversation is carried on through a transmitter and a loudspeaker protected by an iron grille.
Telegrams no longer exist as a service although it survived in a rather feeble form for a number of years before finally being axed quite recently. Still there were a number of cards dedicated to this system in the set. Card 18 shows the teleprinter, a marvel of technology which you rarely see nowadays and is something of a wonder when you do. Card 20 deals with the special requirements of telegrams being sent from the Threadneedle Post Office branch which dealt with the Stock Exchange telegram traffic which had security measures specially adapted to ensure no casual observer would be able to read what could be very sensitive information. Special mobile telegram units were set up at big race meetings.