The letters are still there except they were replaced with numbers. For example; 525 0000 is JA5 0000 JA is the Jackson exchange in Montrose. 862 0000 is UN2 0000 UN is the Underwood exchange in the Heights 222 0000 is CA2 0000 CA is the Capital in downtown. The exchange buildings are still there and I think they still have their old names on them. Hope that helps. There was also a Mowhawk exchange. Maybe google for old houston telephone exchanges. The exchanges were and are large telephone buildings with all the switching equipment.
