Model Railroad Control Systems
Model Railroad Control Systems


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Dispatcher/Operator Telephone board / Electronic Speech Telephone Network board (ASTN)


Download EI14-Isolation-Transformer -
Download EI14-Isolation-Transformer.pdf - Documentation


MRCS-ATSN Version 0.5

First built: 2017-08

This is a Model Railroad Control Systems design by Clint Gilliland, Seth Neumann and John Plocher.

  1. Change headers for external pots to 4 position on ALL 3 pots, so there is a ground on the (new) position 4. Handy if the user has bought some shielded wire and wants to use it on all pots. Should help with noise and RF (cell phone) interference.
  2. Remove C5, was a roll off to prevent pops but really didn’t help
  3. Jumper and new 1K resistor to bring mic preamp down to unit gain for line level input. This is intended for interfacing with line level mic sources such as computer output from Skype for remote dispatching.
  4. Add pads for 100pF monolithic caps on mic in, audio out and both sides of xfmr facing the world. This is to filter out any cell phone interference
  5. Made new component for inexpensive (did I say “cheap?) banggood coupling xmfr and put in parallel with TY145P. Cost reduction.

Bot Silk
Bot Silk
Top Silk
Top Silk

Download - Gerber Fabrication files
Download - Parts List (spreadsheet data)

Parts Value Package Quantity Library Type/Feeder
C2, C6 0.1uF C025-030X050 2x rcl PTH
JP1, JP4, JP8 0.100 1X02_LOCK 3x SPCoast PTH
JP5 0.100 1X03 1x SPCoast PTH
CON1, CON2 0.100 1X04_LOCK 2x SPCoast 2017_04 PTH
SL1, SL2, SL3 0.100 MOLEX-1X4_LOCK 3x SPCoast PTH
JP9 0.200 MSTB2 1x SPCoast PTH
R24 1K AXIAL-0.4 1x SparkFun-Resistors PTH
D1 1N4734A 5.6 V DIODE-ZENER 1x SparkFun-DiscreteSemi PTH
D2 1N5819-B DO41-7.6 1x diode PTH
C3 1uF@50V E2-5 1x rcl PTH
R4 2.2K AXIAL-0.4 1x SparkFun-Resistors PTH
C12 2.2uF MYLAR_CAP C15B9 1x capacitor-wima PTH
Q1 2N4401 TO92-EBC 1x transistor PTH
Q2 2N4403 TO92-CBE 1x transistor-pnp PTH
C1 10 uf @ 50 E2-5 1x rcl PTH
C7 10 uF @ 50V E2-5 1x rcl PTH
R1 10K 3386K 1x bourns_test PTH
R11, R18, R19, R22, R23 10K AXIAL-0.4 5x SparkFun-Resistors PTH
C8, C9 10uF @ 50V E2-5 2x rcl PTH
R9, R10 15K AXIAL-0.4 2x SparkFun-Resistors PTH
R3, R13, R14, R15, R17 22K AXIAL-0.4 5x SparkFun-Resistors PTH
R21 47K AXIAL-0.4 1x SparkFun-Resistors PTH
C14, C15 100 pF C025-030X050 2x rcl PTH
C5, C13 100 pF C050-025X075 2x rcl PTH
C10 100 uF @ 50V E3.5-10 1x rcl PTH
R2, R12 100K 3386K 2x bourns_test PTH
R5, R6, R8, R20 100K AXIAL-0.4 4x SparkFun-Resistors PTH
C11 100uF @ 50V E3.5-10 1x rcl PTH
R7 500K 3386K 1x bourns_test PTH
R16 680 AXIAL-0.4 1x SparkFun-Resistors PTH
C4 .33uF C050-050X075 1x rcl PTH
U$2 EI14_600-600 XFMR580X500 1x MRCSEI14 PTH
JP10 Jameco 101187-RA DCJ0202 1x SPCoast PTH
IC1, IC2 LM324N DIL14 2x linear PTH
J1, J2 RJ14 RJ25-INVERTED 2x SPCoast PTH
JP6, JP7 RS 2168149 AUDIO-JACK-3.5MM_STEREO 2x SPCoast PTH


Dispatcher/Operator Telephone board

Electronic Speech Telephone Network board (ASTN)

(Designed by MRCS)

The Electronic Speech Telephone Network (ASTN) board provides the electronics and connections for building a telephone for a Dispatcher or Operator for use with a model railroad telephone system using either a microphone/speaker/footswitch arrangement or using an inexpensive computer headset. The Mic/Speaker/Foot switch arrangement is recommended where the dispatcher or operator will be in a sound-isolated environment and the headset (preferably noise cancelling) is recommended for Operators and Dispatchers who will be in the layout room. Features include:

  • Supports either Dynamic or Electret microphones
  • Independent control of outbound, inbound and “break-in” volume
  • Break in volume is the level heard by the user when depressing the footswitch (prototype train order operators would break in if there was an error during an order or repeat as a safety measure)
  • Can be used to “modernize” a classic candlestick type phone for better performance in a noisy layout room
  • supports mono or stereo inputs and outputs
  • optional phase reversal on output to help tune maximum volume without feedback
  • No DC load on the dispatcher’s line
  • line level output for powered speakers or input to an external amplifier
  • uses 24 VDC
  • optional remote volume controls
  • transmit LED indicator

This is a Model Railroad Control Systems Telephony design by Clint Gilliland, Seth Neumann and John Plocher.

You are free to download the files and make your own or you can purchase bare boards or assembled and tested product from Model Railroad Control Systems.

This technical documentation is licensed under the Creative Commons Attribution-NonCommercial-ShareAlike