Porthmadog Signal Box was built for the Cambrian Railways in about 1894. It was a Dutton type 2 box, of two storeys with orange-brick locking room walls on a black brick plinth and with the landing and porch under the main roof. Known originally as Portmadoc East, the box had a 14 lever frame. In 1932, the Great Western Railway abolished the West box and extended East to accommodate a new 36-lever 3-bar Vertical Tappet frame. The box closed in 1988 following the introduction of Radio Electronic Token Block signalling on the Cambrian Line and was demolished.

Sources include: Peter Kay, Signalling Atlas and Signal Box Directory (Third Edition), Signalling Record Society, Wallasey, 2010. For further information on the types and designs of signal boxes see: The Signalling Study Group, The Signal Box - A Pictorial History and Guide to Designs, OPC, 1986.

B.A.Malaws, RCAHMW, 26 August 2016.