Bryn Mawr interlocking machine

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Bryn Mawr tower controls the interlocking at Bryn Mawr; the interlocking is an electric interlocking controlled by a Union Switch & Signal Type F machine. The interlocking and tower were placed in service 8/11/1895. Since the primary purpose of the interlocking was to turn rush hour locals, the tower was only open part time, 6:00AM to 10:00PM Monday through Friday except holidays. When the tower was closed, the interlocking was set up to operate in "automatic" mode: the switches had to be lined normal, and the signal levers had to be pulled in the proper direction. Circuitry then caused the signals to behave like automatic block signals.

These photos were taken 5/11/1992, the only time I worked Bryn Mawr on middle trick.

Operator's desk. From left to right: Bell phone, radio, block line patch box, switch box/approach indication lights, block line speaker. The panel blocking device panel is situated above the desk.

Model board. On the lower left of the board is a "mouse trap" switch (like a simple telegraph key) which was used, along with the knob (rotary switch) next to it, to put the interlocking in automatic mode. Beneath the mouse trap is the signal run-down timer. To the right is the dragging equipment detector indicator board/reset panel.

Machine. Unlike later Model 14 electro-pneumatic machines, the case of this machine was wood/glass construction. Several of the switch levers have "Rusty Rail" tags and blocking devices, or "cans," on them, indicating to the operator that the switch cannot be thrown unless the operator is certain that a train is clear of the switch; rust on the rail head may cause the track circuit to not shunt even though the circuit is occupied.

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