sentences:  This was also a cause of isolations early on, but a simple modification restricted the most serious type of failure to a small part of the exchange.The GEC/MOV reeds proved to be the most reliable of all.Once the teething troubles had been largely dealt with, which was not until about 1974, the TXE2s realised more of their expected benefits and it was eventually not uncommon for one Technical Officer to maintain the operation of three of these exchanges, serving perhaps some 5,000–6,000 customers in total.