Field phone and switchboard inter-operability

[Ron King]

Originally Posted by Gary_GJK

I hope a query about line equipment is permissible in a wireless forum!

I am trying to shore up my understanding of line equipment as found in British and Canadian units and formations, particularly for the 1943-45 period. I've not been able to find a single, ideally contemporary, document covering the queries I've set out below, and the myriad pamphlets and working instructions are scarce and expensive - especially for a mechanical idiot like me who can only really comprehend the 'general description' page.

My interest is in the practical/tactical application of signal equipment from Division level down, and knowing what could connect to what is important in defining who could speak to who.

I have been trawling the internet for bits and pieces of info and would appreciate any comments on whether I've at least got the basics right in deciphering which types of telephone were (and were not) compatible with certain switchboards.

Telephones -

Set D Mark V; the field telephone in service in 1939 and remaining so throughout and after the war. Capable of transmitting morse as well as speech. There are a couple of things regarding the D V that I have only recently found myself querying.

It had a buzzer and could only call other phones and switchboards able to receive a buzzer signal. I understand that included the Telephone F and the Switchboard UC6 and UC10 - I don't think it included the Telephone L or J or the Switchboard F & F - is that correct? Also, I found a mention that the 'aural indication' of an incoming call was a buzzing through the handset, is that correct? I have seen the morse key demonstrated as being the means to buzz another phone or switchboard; was the buzzer also used to receive morse transmissions via the handset?

Set F; had no morse capability, being speech only. It had a magneto and could call other telephones or switchboards with magneto receiving capability, and also had a buzzer so could communicate with a D V. A high power version of the F with amplifier available for longer distances, seemingly phone to phone rather than via a switchboard.

Set L; later war telephone, speech only, I think initially intended for linemen but latterly issued as unit equipment. I think this only had magneto call/receive, so could not operate direct to a D V unless via a compatible switchboard?

Set J; late/post war period, designed for tropical climates, otherwise same outline as for L.

Switchboards -

Universal Call; 10 or 6 line versions, could receive calls by magneto (as in Tel F) or buzzer (as in D V).

Switchboard, magneto, 10-line (WD); late war development for tropical theatres, which dispensed with the buzzer so could not receive from a D V, only from magneto phones. Required a phone L or J to be connected to it for operator use.

Switchboard, F & F (field and fortress); used in Div Sigs Operating Sec/Tp.
Built up from a 5-line unit, with four units housed in a cabinet to make a 20-line switchboard; could have one, two or three cabinets so fitted giving 20, 40 or 60-line capacity. I think this only worked to magneto phones, so fine with the F, L and later J telephones but not the D Mark V.

Any comments appreciated.

Thanks,

Gary

I have recently acquired various field phones and trying to sort out the same questions
I have 2x 1918 model.D mk2 buzzer units....extremely fragile due to age.......but I think I will get them going.......L1 ..and then CL and then LorE..........three connections has got me lost
Have a model L that works and about 4x Model F mk2 that work.( trying to get another Two working)
I am guessing buzzer phones may still ring /buzz bell on some magneto phones.
Have Australian 10 line no2 switch board.......similar to the UC10.
Relay indicator flaps on switch board are very sensitive.........buzzer phone should trip them.
This is all a new item of learning for me.........challenge to get them working.
Ron.

[Gary_GJK]

Thanks all for the above, especially Chris for going through the various types of phone and switchboard. I'm still hoping to finish my write-up for WW2 era Inf and Armd Div Sigs, and having spent a lot of time on wireless realised I hadn't put much effort into line equipment. The differentiation between buzzer and magneto calling/receiving was something I only recently recognised and encouraged me to go dig more into the subject.

Cheers,

Gary

[Chris Suslowicz]

Originally Posted by Ron King

I have recently acquired various field phones and trying to sort out the same questions
I have 2x 1918 model.D mk2 buzzer units....extremely fragile due to age.......but I think I will get them going.......L1 ..and then CL and then LorE..........three connections has got me lost

Ah! This is fairly simple:

L1 is the telephone line
L or E is the other telephone wire if it's a pair, or Earth if you're using a single wire and earth return (wire to a ground spike "Pins, Earth, Small" or the "heel attachment" on one of your boots - the latter was mainly for line-laying parties).
CL is "Condenser to Line" - for "piggybacking" a telephone circuit on a DC Telegraph wire (usually railway telegraphs in the outer parts of the Empire); it blocks the DC signalling voltage and prevents interference to the Telegraph or the telegraph traffic causing interference to the telephone.

There should be circuit diagrams for the D2 in "Instruction in Army Telegraphy and Telephony Volume 1 - Instruments" the second (1916) edition is probably the best. WS19 group has a copy in the archive. (I've still not found the Signal Training Part III (Instruments) that followed it.)

https://royalsignals.org.uk/signals.htm

(Follow the instructions on the main page when requesting documents; it's a bit fiddly due to relentless abuse by various pirates, etc.)

Have a model L that works and about 4x Model F mk2 that work.( trying to get another Two working)
I am guessing buzzer phones may still ring /buzz bell on some magneto phones.

This is very unlikely. The early "Buzzer Switchboards" used a "Watch Receiver" (i.e. earpiece) to alert the operator. The Telephone Sets 'D' (all marks) were similar, with a single earpiece on a headband for the operator to wear continuously. The D Mark V added a magneto bell for compatibility, and the Mark V* deleted the single earpiece (and should have a wire link across the terminals or the handset earpiece won't work).

Have Australian 10 line no2 switch board.......similar to the UC10.
Relay indicator flaps on switch board are very sensitive.........buzzer phone should trip them.

The Switchboard "Universal Call" (6 or 10 line) was designed to work with both buzzer and magneto calling, but the relays/indicators need careful setting up - there should be "go" and "no-go" resistors clipped inside for setup purposes (to ensure the indicators operate with a buzzer call).

This is all a new item of learning for me.........challenge to get them working.
Ron.

Have fun!

Chris.

[Ron King]

Thank very much for those gems of information
Regards
Ron.

[Ed Storey]

Attached is a 1941 image of some Set D Telephones in use by the RCA in England.

DSCN3197 [1] copy.jpg

[Chris Suslowicz]

Hmm... three Telephone sets 'D' Mk.V (which look like the Canadian version with cast-aluminium rather than the British pressed steel cases), something I don't recognise but may be a small buzzer switchboard[1] for the telephones, and an Apparatus LoudSpeaking on the right, with two 6V 85AH accumulators to power it. It's the 4-channel version, so probably for a 4 x 25pdr gun battery.

Nice photo.

Chris.
[1] Somewhere I have a "3-line switch unit", allegedly for Artillery use, but it has Kellogg keys and doesn't (I think) look like the one in the photograph. So: a phone for each member of the team plus the ALS for the Gun Position Officer, and presumably lines to the FOO and the unit commander?

[Ed Storey]

In 1941 the 1st Medium Regiment was equipped with B.L. 6-Inch 26 cwt Howitzers.

DSCN3191 [1] copy.jpg