What was found
BWI - FL2785 - ON CLIMB-OUT FROM IAD, AT FL170, THE 'B' HYDRAULIC SYSTEM BRAKE PRESSURE INDICATOR FAILED AND INDICATED ZERO. ALL OTHER HYDRAULIC INDICATIONS WERE NORMAL. CAPTAIN ELECTED TO DIVERT TO BWI AND DECLARE EMERGENCY. FLIGHT LANDED WITHOUT INCIDENT AND TAXIED TO THE GATE ON ITS OWN POWER. PASSENGERS DEPLANED NORMALLY. MAINTENANCE REMOVED AND REPLACED THE 'B' HYDRAULIC SYSTEM BRAKE SYSTEM BRAKE PRESSURE TRANSMITTER. OPERATIONAL CHECK GOOD. (M)