There are many career opportunities in railway signalling and telecommunications in many countries. The range of activities is enormous, encompassing the latest software-based systems as well as "heritage" equipment. You might be interested in specification, design, installation, testing, maintenance, project engineering, research, product/system development ... the list is long. There is scope for people interested in electrical, electronic, mechanical and software engineering and information technology, as well as specialists in safety engineering, RAMS and human factors.
How and what to study
Typically members follow a course in electrical or electronic engineering, physics or safety engineering. Courses can be vocational, technical or academic in nature. Your employer may sponsor you to attend a course, or to be an apprentice, or to join its own engineering training scheme.
Finding a job
Advertisements for jobs are contained in IRSE NEWS (the Institutions's monthly magazine distributed to all members) and on the Jobs Board on this website).
In the UK
Specifically in the UK, you might like to look at the following websites:
Routes into Rail
Plotr - Transport World
Controlling Trains (YouTube)