This relay set receives alarm conditions from up to five outstations and displays the conditions on lamps on the C Unit.

It also sends 30 sec clock puilses to the five outstations, allowing Norchard time to be displayed at those points.

Parkend

This arrangement normally maintains a 50 volt negative battery on the alarm extension wire (the other wire of the pair is used to extend clock pulses from Norchard to Parkend). This battery holds relay NB at Norchard operated and the green "normal" lamp lit on the U13 C unit alarm panel.

Should a prompt alarm occur at Parkend, or the cable pair go "dis", then the negative battery is removed and NB releases to dim the green "normal" lamp and light the red "prompt alarm" lamp.

If a deferred alarm occurs then the negative battery is replaced with a positive battery and relay PB operates in place of NB and this lights the white "deferred alarm" lamp at Norchard.

The clock pulse is a 1500 ohm battery extended on the second wire of the pair to Parkend.

Other Outstations

The alarm reception is similar but only permits the reception of prompt alarms. The clock pulse transission is also similar but is a 1000 ohm battery pulse.

Page provided by John Bathgate This page was last updated on 5th May 2011