Model Forum / General / Railroads / September 2009

Perhaps this might help

http://www.railway-models.co.uk/1343_1_1039802.html

The arch shaped piece with the hole is in all probability the fret for a
fireman's call plunger sign.

The majority of signs that are affixed to signal posts, or near signals, are
of significance to drivers detained at the signal awaiting its clearance. In
the old Rule Book, Rule 55 dealt with the actions to be taken upon the
detention of trains on running lines. This began:

"When a train has been brought to a stand owing to a stop signal being at
Danger the Driver must sound the engine whistle, and, if still detained, the
Guard, Shunter or Fireman must go to the signal box and remind the Signalman
of the position of the train..."

     At some locations the walk from the signal to the signal box would
have been time consuming or hazardous. To overcome this, the 'Fireman's Call
Box' was introduced. When the fireman pressed a plunger at the call box, an
indicator in the signal box was operated. If the equipment had functioned
correctly, a bell rang in the call box and the fireman was exempt from going
to the signal box. The equipment was trialled and proved to be successful
and rapidly spread. To indicate the presence of the fireman's call box, an
illuminated sign was provided. At some signals, drivers were exempt from
carrying out the requirements of Rule 55 due to there being a track circuit
or other form of train protection that would automatically indicate the
presence of the train to the signalman. This was denoted by an illuminated
sign fixed at or near the signal concerned. Because these signs were
illuminated, they needed their own separate lamp in addition to the signal
lamp. The Midland Railway avoided the provision of separate lamps by fitting
non-illuminated plates instead. By 1912, they had introduced the 'D' sign to
denote that a fireman's call plunger was provided for the driver or fireman
to remind the signalman of the presence of the train.

     It was fixed roughly half way up the post, face to the running line,
showing as a white D, with the "arch" to the side. The post to which it was
affixed was usually painted black behind the sign and for a few inches above
and below the D. It would not be used on a distant signal since there would
generally be no requirement to stop at a distant.

     Hope this helps.

     Archie