. Electric railway journal . grouped, that it is impracticableto attempt automatic operation of the switches. Thesepoints of congestion will be found to have a car head-way of from forty-five seconds to one and one-quarterminutes. In most cases the operation by switchmen isattended with difficulties, such as dodging cars andvehicles and at some personal risk. These conditionsare overcome by the use of tower or curb control devicesused in conjunction with the switch-throwing mech-anisms of the automatic type. These control devicesare shown in Fig. 10. The tower control consists of a switch cont
. Electric railway journal . grouped, that it is impracticableto attempt automatic operation of the switches. Thesepoints of congestion will be found to have a car head-way of from forty-five seconds to one and one-quarterminutes. In most cases the operation by switchmen isattended with difficulties, such as dodging cars andvehicles and at some personal risk. These conditionsare overcome by the use of tower or curb control devicesused in conjunction with the switch-throwing mech-anisms of the automatic type. These control devicesare shown in Fig. 10. The tower control consists of a switch control cabinetand resistance board. The operator has in front ofhim in the tower an indicator board upon which ismounted a model layout of the track and switches, eachmodel switch being electrically operated by contactsin the real switch into positions always in correspond-ence with its own. Mounted on the control cabinet arecontrol handles, one for each switch and numbered thesame as the model switches on the indicator SHOWING PROVISION FOR DRAINAGE The handles have a rotary movement of about 60 deg.,.being locked in position by a simple latch which theoperator must lift to move the handle, thus preventingunintentional movement. Each handle operates a camwhich in turn engages a swinging latch of a magneticblow-out, quick-break switch which makes and breaksthe circuits to the solenoids in the switch-throwingmechanisms in the street, throwing the switch in thedirection in which the control handle is rotated. Wiringdiagrams of tower control and curb control installationsare shown in Fig. 11. In cases where the operator has many switches to- October 19, 1918 Clear the Track for Berlin 693 handle it becomes advisable to lock the control handleso that it cannot be moved while a car is passing overthe switch. This is prevented by installing two smallcontactors in advance of the frog on the wire. Thefirst locks the handle by means of a small magnetmounted on the control cabinet a
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