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Ericsson field telephone M3926-384011

Directions & Operating Notes

Translated with notes by Had Robinson www.southwestairsports.com

The original telephone came with the following accessories: a.) Dialer b.) Handset c.) Extra receiver d.) Hand tool (upper right) e.) Instructions (in Swedish).  On the surplus market all or none of these accessories may be present with the set.

Ericsson field telephone M3926-384011

 Ericsson's review (1935) of this set has extensive information on its features and how it should be used during wartime.

Connections

NOTE: The LB–CB selector knob must be set correctly (see below) before connecting the field telephone to the telephone network via terminals La and Lb.  It does not matter which terminal is used to connect to the network as the set is not polarized.

The handset holder (Klyka), the LB–CB selector, and latch bar (Spärr) are illustrated in these photos and also in figure 1 (Bild 1) below.

1. The telephone may be connected to a central station network (e.g. ATT) or directly to other field telephones.  Connect the wires to terminals La and Lb.  These telephones will not work on digital networks.

2. The extra receiver may be connected to the instrument per this photo.  There are (2) sets of jacks that can be used.  The extra receiver permits a third party to monitor the telephone conversation.

3.  When used on a central station network, the dialer may be connected to the instrument per this photo.

LB – Local telephone network operation (not connected to a central station network)

1. The selector knob must be in the LB position.  If it is in the CB position, do the following:

a.  Pull the latch bar (Spärr) straight out and hold it.
b.  Press down the selector knob and turn to position LB.
c.  Let the latch bar spring back and lock the selector latch bolt (Spärrbult) in position.

2. The button on the handset must be depressed when speaking in order for the other party to hear. It can be released when listening or held for the entire call.

3. Making a Call – Ring the other field telephone(s) on the network by turning the hand crank.  It is easy to send codes via the ringer e.g. one long, two short rings so that a user can know if the call is for him.

4. Receiving a Call – Wait until the ring signal stops and THEN lift the handset to the ear to avoid injury to the ear by the very loud ring signal.

5. Ending a Call – Return the handset to the holder (though this is not necessary in LB mode).

CB – Central station telephone network operation (a public telephone network e.g. ATT)

1. The selector knob must be in the CB position.  If it is in the LB position, do the following:

a.  Pull the latch bar (Spärr) straight out and hold it.
b.  Turn the selector knob to position CB.  (It will move to its upper position.)
c.  Let the latch bar spring back and lock the selector latch bolt (Spärrbult) in position.

2. The button on the handset must be depressed when speaking in order for the other party to hear. It can be released when listening or held for the entire call.

3. Making a Call – Remove handset, press the selector knob down, and check for dial tone.  Use dialer as needed.  Note: these telephones will NOT work on digital phone systems.

4. Receiving a Call – The ringer will sound until the handset is lifted and the selector knob is pressed to its lower (locked) position.

5. Ending a Call – Return the handset to the holder.  The selector knob will pop up to its upper position.

6. Do NOT use the hand crank at any time when the telephone is connected to a central station network.  The central station, not the telephone originating the call, supplies the ring signal to the other telephone.

Miscellaneous

1. Place the handset is in the holder when the telephone is not in use.  In doing this you will know that the selector knob is in the correct position (up) to receive a call when in CB mode. 

2. Do not hold the handset to the ear when making any changes with the selector knob as the DC impulses (clicks) are very loud. 

3. The knob labeled “S” is used for voice-frequency telegraphy in the same manner as a telegraph key.  As Ericsson notes in its review of the set, the presence of a tone generator allows the user to employ voice-frequency telegraphy when speech is unintelligible or background noise is excessive. 

4. The set requires (2) "D" sized batteries.  See figure 2 (Bild 2) for correct battery placement.  A small voltage is necessary for the microphone to function.  You cannot be heard by others if you do not install the batteries.  The set is not polarized so that the battery holder may be installed with the diagram facing in or out.  If it is placed facing out, it is easier to see if the battery holder is installed or not.  The use of lithium batteries is recommended as they will last for many years and not leak.

5. The set has a small tool stowed near the hand crank which can be used to disassemble the telephone (remove it from the case).  One end has a socket which, presumably, is for use on ordinary Swedish phone terminals.  I do not recommend using the tool to undo the (3) screws that hold the set in its case because the screws slots are much larger than the tool's blade.  If the screws are not torqued firmly, they can loosen.  We discovered this hauling these telephones through deep caves.

6. During inclement weather, the set can be used in LB mode by replacing the cover and dressing the cables through the small openings beneath the latches.

Figures (Bild) 1 & 2

Ericsson field telephone figure 1

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