Dual channel sound at Channel Four [TV station]

Channel Four is a national TV network, broadcasting on average 20 hours per day. The addition of a second level of audio presented a wide variety of problems and has involved a major rebuild of in-house facilities and distribution systems as well as the incorporation of larger central routing and network switching systems. These major changes were complicated by the need to convert both main and standby presentation mixers plus the MCR emergency switcher to stereo; equip incoming and outgoing BT lines with DCS equipment and install stereo processing units on the output of every VTR