Tools of Telegraphy Page 2
Page 1- Leg Key, Legless Key, Local Sounder, Mainline Sounder
Page 2- Morse Relay, Bug, KOB, Box Relay
Page 3- Barclay Box Relay, Candlestick Resonator, Swing-arm Resonator, Cordless Jackbox
Page 4- Sideswiper, Repeater, Polar Sounder, Register, Gravity Battery, Insulators
The relay is a very sensitive "amplifier" of the weak currents found in long distance telegraph circuits. Two horizontal solenoids wound with fine wire form a horseshoe magnet. This magnet is connected in series with the telegraph wire. Current in the wire causes a magnetic field to attract the lightweight armature, which is suspended vertically. The armature has one side of the relay contact-- the other side of the contact is on the adjustable screw in the "gooseneck". The fact that the armature is suspended vertically with its bearings on the relay base makes it extremely unstable. A very light force is applied by a spring, which is adjusted by a "windlass". The spring tension keeps the contacts open until the magnetic force exerted on the armature overcomes it, thereby closing the contacts. The spacing of the magnet from the armature is easily adjusted by a knurled knob. The magnet spacing plus the spring tension is easily adjusted to allow for variations in line current. Line current decreases dramatically during wet weather, thus the relay provides for a wide range of sensitivity. The relay's contacts are connected to a "local circuit". See the local sounder below for a description of the local circuit. This relay is a Western Union model 4-C 25 ohm relay, however, it was probably not manufactured by Western Union.
Semi-automatic Key or "Bug"
This is a semiautomatic key or "bug". This key was invented by Horace Martin in 1904. The key is operated by side-to-side movements of the fingers, as opposed to previous keys which used up-and-down motion. A vibrating metal strip generates dots when the paddle is moved to the right. Dashes are generated manually by moving the paddle to the left. This design greatly reduced the motions required to generate Morse characters. This helped alleviate the telegrapher's "glass arm" which today is known as "repetitive motion syndrome" or "carpal tunnel syndrome". Although it was intended to make sending easier, it also increased the average speed at which a telegrapher could transmit Morse compared to what could be done with a manual key. This particular bug is a Vibroplex company "Original". This is the japanned base version, and the serial number is 98699. The device attached to the cord is called a "wedge". The wedge is a very early version of an electrical plug. It is inserted into the circuit closer contact in an ordinary straight key, thus allowing the bug to be easily connected to any circuit. Most operators owned their own bug and adjusted it to their liking.
Key On Board
A "Key On Board" or "KOB" set. This set consists of a leg style key and a telegraph sounder attached to a wooden base. The key and sounder are connected in series, and the connections to the telegraph wire are made to the two binding posts at the rear of the board. This makes for a reasonably compact portable set. Most KOBs found today are "practice sets". A practice set is a relatively cheaply made KOB intended for practicing the sending and receiving of Morse. Common practice sets may be distinguished from professional sets by the three binding posts. Thus three wires connected the two sets. This allowed the use of dry cell batteries without quickly draining them as would occur with a closed circuit telegraph. This KOB was made by Bunnell, and it has a 20 ohm 1895 pattern sounder with the standard Bunnell steel lever leg key.
The "box relay" is an interesting adaptation of the Morse relay. A wooden box is formed around the magnets. Where the fixed relay contact would be attached to the brass "gooseneck", the box relay's contact is attached to the wooden box. The light clicking sound you would normally hear from a relay is amplified by the resonant cavity of the box. So now you have a receiving device that is extremely sensitive, and yet it is loud enough to use in relatively quiet locations. This made the box relay a good choice for portable or temporary telegraph offices. The box relay could be considered the predecessor of the mainline sounder.
Some box relays did in fact have functional contacts and could be used with a local sounder. This well used example was made by Bunnell. The slight tilt seen in the photo is due to the leg key which has the long bolts. This is probably not the original key that came with the set. I suspect the original key had been removed, only to later be replaced with a correct type key but incorrect bolt length. The metal lable indicates 20 ohm resistance, however it measures 150 ohms. I suspect the "restorer" used the label from a 20 ohm relay to replace the lost label.
Go to Page 3 of Tools of Telegraphy
QSY to Telegraph Lore Home Page