All the TXE2-specific equipment was mounted on slide-in units, mainly single-width, but some double-width. There was a structured holding of maintenance spare units. For those which were likely to be needed frequently or urgently in every exchange, such as a Subscribers Line Unit, a spare unit was held in every exchange. For those units for which a spare was likely to be needed less frequently or urgently, the spares were held at an Area centre serving perhaps 6–10 TXE2s of the same manufacture. Finally for those units for which a spare was likely to be needed seldom, the spare units were held at one centre per Region - there being ten Regions in the UK.