Jack Wabbit Derivatives Explained

Jack Discrete Sensor
The Jack Discrete Sensor is designed to work only with Digitrax LocoNet Systems. The Jack Discrete Sensor is a derivative of the Jack Wabbit Quad decoder that takes advantage of the Jack Wabbit LocoNet interface and the ability of the Jack Wabbit to read both discrete inputs and DCC voltages.  The Jack Discrete Sensor can read any combination of up to 8 discrete or DCC inputs. Whenever an input changes state (e.g. on/off, DCC present/absent), a General Sensor Input message is sent on LocoNet indicating the address of the changed sensor and the new state of the sensor.

The Jack Discrete Sensor is designed to provide layout status information to automation programs such as JMRI via the LocoNet. Note the sensor messages are not available for display on the throttle, but are available to the automation software for layout control. Sensor inputs can include block detectors, manual toggle switches, Tortoise or other switch machine position switches, optical couplers, or almost any type of sensor that provides an on/off switch contact. Unlike other available LocoNet interfaces, the Jack Discrete also has inputs that can be directly connected to the DCC bus or track. These inputs detect the presence or absence of DCC and can be used to sense the power status of a power district (on/off) by direct connection to the bus or track. Another use is train sensing using a trigger rail. You can isolate a short section of rail (1/2” to 1” for example) and connect it to a DCC sensing input on the Jack Discrete. When the engine bridges the isolated track to the main track, the trigger rail is connected to DCC and a message is sent on LocoNet which can be used by the automation software to determine a specific engine position.

Many DCC Specialties products have feedback outputs. The Jack Discrete is specifically designed to allow you to connect these devices to LocoNet for use by your automation software. The Hare and Wabbit can use the Jack Discrete to report switch position (the Jack Wabbit will report position directly), while the PSX and PSX-AR can report output power status, short status, and block occupied for use by your control software.

Each Jack Discrete occupies 4 LocoNet addresses and will provide a total of 8 sensor status input to LocoNet. The inputs can be 8 discretes, 8 DCC signals, or any combination of discrete and DCC that totals 8. Multiple Jack Discretes can be used simply by giving each one a unique LocoNet address.

Jack Discrete Absolute

The Jack Discrete absolute is designed to work only with Digitrax LocoNet Systems and is virtually identical to the Jack Discrete Sensor except that it sends a Turnout Sensor State message instead of a General Sensor message. This means that the message is intended for display on your throttle rather than for use by automation software.

The ability to display absolute position information on your throttle is an important function when you use DCC Specialties switch control products. The Digitrax throttle remembers the last DCC point position command, which will work if you only use DCC commands. However, the Hare and Wabbit can change point position without a DCC command (manual control inputs and autothrow) which will make the throttle displayed point position incorrect. With the feedback outputs connected to a Jack Discrete Absolute, the point position reported by the throttle will always be correct regardless of the point change method. Note that in some instances that the throttle SWCH button must be presses to get the throttle to update the display.

While primarily intended for switch position reporting, the Jack Discrete Absolute can also be used with the PSX breaker and PSX-AR. You can use your throttle to tell you if a PSX is on or off, shorted or not, and whether the photo cell function is armed or not by tying the appropriate PSX feedback outputs to a Jack Discrete Absolute.

Sherlock Wabbit

The Sherlock Wabbit is a position detecting (pun intended) device specifically designed to work with the NCE Mini Panel. It can signal condition up to 8 photo cells located between the ties of the track and provides 8 triggers to the NCE Mini Panel, one per sensor. This means you can use up to four Sherlock Wabbits with one Mini Panel. The combination of the Sherlock Wabbit with the NCE Mini Panel provides you with very powerful control of your layout. The optical sensors can provide a trigger either when they cover or uncover, and the Mini Panel can send an almost unlimited set of DCC commands based on the trigger input. The optical sensors are self-calibrating to the ambient light level present at power on. There is no need to mess with “sensitivity” adjustments. In very dark locations, a light source as small as a grain of wheat bulb is sufficient to operate the sensors.

Starting simply, you can use the Sherlock Wabbit/NCE Mini Panel combo to make a point to point railroad such as a trolley run. A sensor at each end triggers the Mini Panel to send a string of DCC commands that tells the train “slow down, stop, then startup in the other direction”. While that is a great start, you can also add sensors along the way and have the train stop at intermediate stations, wait, and then startup again, including (literally) bells and whistles.

Since the combination can send DCC commands when the train is in a particular position, you can use it to set up a particular switch pattern when a train reaches a certain position. This can keep you from running mis-aligned points or route you through a complex route.

Basically, any function you do with your NCE throttle, you can now do automatically based on a train entering or leaving a particular location.

Jack Light

The Jack Light is a Jack Wabbit Quad switch controller that has all of the features the Jack Wabbit, but instead of the manual switch and auto throw inputs, the Jack Light has optical sensors similar to those used in the Sherlock Wabbit (above). Further, each switch output and its associated LED outputs have a 16 CV array telling the switch driver and LEDs what to do for each sensor when it covers or uncovers (two states for each sensor times 8 sensors is 16 CVs). The choices for switches are: No Change (the default), Clear, Throw. The choices for the LEDs are No Change (the default), Green, Red. There is a CV that allows you to lock the signal indication to the point position or have it be completely independent.

The idea of the Jack Light is that you can use it to sequence a train through a section of your layout (such as a yard or passenger platforms) including operating red/green signaling to hold a second train after a train has entered the section controlled by the Jack Light. A simple application could keep trains from running mis-aligned points. A sensor in the clear route would be programmed to move the points to clear when it covered. Similarly, a sensor in the throw route would be programmed to throw when covered. A train approaching against the point position would cause the points to align with the train when it crossed the sensor. In this case, the LED outputs would be locked to the point position.

If you have a yard with a particular traffic flow, a sensor at the start of the flow can align switches for incoming trains while setting signals to red to keep others out. As the train proceeds through the yard path, switches can align to ensure the train follows the correct route and signals set appropriately to stop following trains. Using an “uncover” sensor where the train leaves the yard can clear all for the next train.

If you have a reverse loop that you want to always use in the same direction, you use an entrance sensor to always align the desired entry direction, then use an exit sensor to move the exit switch to the correct position as the train comes around.

Basically, the Jack Light has application in any area that requires a particular traffic flow entering and/or leaving a particular section of track.