DFR - Diagrams in PDF Form
Cinderford Exchange etc
This is a 22 line 4000 type exchange that could be used at the far north of any extension to the railway. Construction has started. The equipment is being designed so that the exchange will be very versatile. It will work as a stand alone unit or it could be integrated into the DFR linked numbering scheme. All outgoing junction calls will be regenerated as the junction cable length will be rather long.
Lydney Junction Exchange etc.
This is a simple uniselector 22 line exchange. The uniselector line finder extends a caller to Norchard and the Norchard first selector provides dial tone. Any one dialling a 6 is connected to a junction incoming to Lydney Junction and the two final digits are used to position a uniselector onto the called number's line circuit. Local calls on the Lydney Junction exchange are therefore connected via junctions to and from Norchard. This was known as trombone working.
Norchard Exchange etc.
The exchange is basically a standard UAX13, however many locally designed selectors and relay sets have been added for various purposes over the years and these diagrams are listed below. The standard UAX13 diagrams are not shown here.
Parkend Exchange etc.
The exchange has been constructed mostly from PABX4 equipment, however many locally designed selectors and relay sets have been added for various purposes over the years and these diagrams are listed below.
Parkend North Exchange etc.
This 22 line uniselector exchange is not yet in service. It is complete and waiting installation in Parkend Signal Box. It has been designed specifically to allow long lines to be connected to it and so will be available to service any lines going north from Parkend as the railway extends. It is very similar in circuit design to Lydney Junction Exchange but has been physically constructed somewhat differently. All outgoing calls will be made via first selectors in Parkend exchange. Incoming calls will arrive via junctions from both Norchard and Parkend.
STARS (Signals and Telecoms Alarm Reception System) collects alarms from around the railway and directs them back to Norchard. Any alarm is first displayed by the appropriate lamp lighting on a simple display at Norchard exchange. If the alarm persists for more than six minutes it then lights a lamp in a key and lamp display in the shop office. The appropriate officer can then be informed of the alarm condition. The system is notable for the way in which up to three alarm locations can be combined to transmit alarm signals over a single wire to Norchard.
NORCHARD PUBLIC ADDRESS EQUIPMENT
The public address equipment is quite complicated as access to the amplifier is required from two microphone positions and from several telephones around the site. These telephones gain access to the amplifier by dialling a Norchard number and by also pressing a button which puts a loop on a control pair. The amplifier is also accessed on a high priority basis by the fire warning equipment to distribute a warning tone, and by a CD player with very low priority to provide background music when required.
NORCHARD FIRE WARNING EQUIPMENT
The Fire Warning equipment was designed as an interim system until a regular fire alarm system could be installed by our alarm contractor. The equipment is still in use. Essentially, if any one on the Norchard site dials a given number on an internal phone, then the warning system provides a warbling tone over the PA system for one minute. The originator can hang up and dial other numbers while the one minute tone is sounding. The two microphones connected to the PA system have priority over the warbling tone so that instructions can be issued over the PA.
The Clocks at Norchard are controlled by a standard GPO pendulum master clock. A second master is available and can be switched in should there be a difficulty. We have three types of clock in use.
1) the usual 30 second pulse clocks that are connected in series within the main building.
2) clocks that are driven over separate pairs by a 50 volt supply that reverses every 30 seconds.
3) pulse clocks that are remote from the main building and need to be fed via separate pairs with a 30 second pulse.
4) the 30 second pulses are also fed to Parkend and Lydney Junction over the second wire of the alarm/clock pair.
Page provided by John Bathgate
This page was last updated on
10th September 2017