Some of the common track circuit ailments are relay and track battery troubles, defective track connections, poor bonding and broken rails, short circuits or shunts, excessive leakage and defective insulated joints, all of which will cause the signals to be set in the danger position, while defective relays, foreign current and poor wheel contact may result in a false proceed signal indication with a train in the block section. It was the quite general practice to operate bad track circuits by piling on gravity battery, either in multiple or multiple-series arrangements to obtain operating results without any regard to the safety of the circuit and, no doubt, many false proceed failures were caused thereby. The effect of temperature changes on track circuit operation are of considerable importance. The track relay, which is generally housed in a cast or sheet iron box, probably is affected more by changes in temperature than any other part of the track circuit. The resistance of a 2-ohm relay, which is 2 ohm at 70 degrees F., will be 2.22 ohm at 120 degrees F., and 1.69 ohm at 0 degrees F., a variation of .53 ohm. The pick up and release of the relay, .2 and .1 volt, respectively, at 70 degrees F., will be .22 and .11 volt at 120 degrees F., and .17 and .085 volt at 0 degrees F. A relay, with a normal resistance of 4 ohm at 70 degrees F., will be 4.45 ohm at 120 degrees F. and 3.38 ohm at 0 degrees F., a variation of 1.07 ohm. The pick up and release, .3 and .14 volt, respectively, at 70 degrees F., will be .33 and .16 volt at 120 degrees F. and .25 and .12 volt at zero. The point which is intended to be brought out by these figures is that when the temperature of the relay increases, a correspondingly higher voltage is required to pick up the armature, and when the temperature decreases the armature will hold up with lower voltage across the coils. This indicates that a track relay is more liable to fail to release due to an imperfect train shunt in cold weather than at any other time. Some of the best preventatives that may be provided to guard against false proceed signals due to track relays failing to release with a train in the circuit, are: 1. Use as much resistance as practicable between battery and track. 2. Use low resistance bond wires, and maintain bonding in good shape. 3. Keep ballast well cleared from contact with rails. 4. Maintain insulation in insulated track joints in good condition. Aside from these simple remedies no definite rule can be given to combat foreign current. If it is so troublesome that these methods do not overcome it, the circuit affected must be carefully studied to determine the source of the foreign current and its path to the rails, then special means can usually be provided to overcome it. Ballast Resistance and Leakage