It is important the board isn't lying on metal or conductive when powered up, to prevent shorting out the board.

If you plan to interlink two boards, see the "Interlink" section of this document.

Free Standing
If the board is not mounted to a backboard yet, place the board on a non-conducting surface
(wood, cardboard, etc) that is free of metal parts that could short out the board, e.g.
no staples, paperclips, stray screws/nuts/wire clippings, etc.

Mounting to a Backboard
If mounting the KSU to a backboard, use screws through all mounting holes with standoffs
to keep the board elevated off the backboard's surface, so air can flow along the back
to aid in cooling of components, and to prevent catching stray metal (like wire clippings).

: : ──▷: :◁── 1/4" or more : : : ░░░░░░░ : ░░░░░░░ : ░░░░░░░ ▒▒ ░░░░░░░ ▕╰▒▒────░░░░░░░ ┌─────▶ ▕╭▒▒────░░░░░░░ │ ▒▒ ░░░░░░░ │ ▒▒ ░░░░░░░ │ ▒▒ ░░░░░░░ Mounting │ ▒▒ ░░░░░░░ Screws ─────┤ ▒▒ ░░░░░░░ │ ▒▒ ░░░░░░░ │ ▒▒ ░░░░░░░ │ ▒▒ ░░░░░░░ │ ▕╰▒▒────░░░░░░░ └─────▶ ▕╭▒▒────░░░░░░░ ▒▒ ╱ ░░░░░░░ ╱ ╱ ░░░░░░░╲ KSU Board ▁╱ ╱ ░░░░░░░ ╲▁ Backboard ╱ ░░░░░░░ (fire retardant) Standoffs ▁╱ ░░░░░░░ Figure A: Side view of KSU board mounted to backboard. Standoffs can be metal, nylon, rubber, etc.

If metal standoffs are used, make sure their diameter does not exceed the diameter of
the white circles around the mounting holes, to prevent shorting traces on the board.

For rubber standoffs, insulation from outdoor extension cords can even be used, e.g.


Figure A2. Side view of actual installation on fire retardant plywood backboard with yellow rubber standoffs made from an outdoor extension cord. NOTE: Use screws in all 7 screw mounting hole positions provided. Not just around the corners,
but the ones in the center as well. Center screws prevent boards from bending when plugging/unplugging
the large 50 pin Amphenol connectors, which would otherwise mechanically stress solder traces.

Connect power by plugging in the 12volt power:

____________________________________________________________________ | ::::::: INTERLINK | | EXT1 EXT2 EXT3 EXT4 | | o o o o A | | LINE1 CPU LINE2 ICM : B ╱▔▏ ╱▔▏ ╱▔▏ ╱▔▏ | | STATUS STATUS STATUS STATUS : : ▏ ▏ ▏ ▏ ▏ ▏ ▏ ▏ | | : : ▏ ▏ ▏ ▏ ▏ ▏ ▏ ▏ | | o CPU2 : : ▏ ▏ ▏ ▏ ▏ ▏ ▏ ▏ | | STATUS : : ▏ ▏ ▏ ▏ ▏ ▏ ▏ ▏ | | : ▏ ▏ ▏ ▏ ▏ ▏ ▏ ▏ | | ___ __ ____ ____ ╲_▏ ╲_▏ ╲_▏ ╲_▏ | | | | |+-| |oooo| |oooo| | |__|___|____|__|____|____|_____________|____|________________________| Line1+2 12VDC Ring Trig. Ext Ring (RJ-11) Power Connector Gen Power ▲ ╱┃╲ ┃ ┃ ......................................................... : Attach 12VDC power here. POSITIVE on LEFT. : : NEGATIVE on RIGHT. Must be 850mA minimum. : : The stock 2.5 amp supply can drive 2 boards/8 phones. : :.......................................................: ▘▘▘▘▘▘▘▘▘▘▘▘▘▘▘▘▘▘▘▘▘▘▘▘▘▘▘▘▘▘▘▘▘▘▘▘▘▘▘▘▘▘▘▘▘▘▘▘▘▘▘▘▘▘▘▘▘▘▘▘▘▘▘▘▘▘▘▘▘▘▘▘▘▘▘▘▘▘▘▘ ▘ IMPORTANT ▘ ▘ If you wired the connector yourself: MAKE SURE POLARITY IS CORRECT! ▘ ▘ DO NOT CONNECT 12V POWER WITH POLARITY REVERSED, IT WILL KILL THE CARD. ▘ ▘ This board has NO PROTECTION against reverse polarity DC power; ▘ ▘ it will blow random components on the board if polarity is reversed. ▘ ▘▘▘▘▘▘▘▘▘▘▘▘▘▘▘▘▘▘▘▘▘▘▘▘▘▘▘▘▘▘▘▘▘▘▘▘▘▘▘▘▘▘▘▘▘▘▘▘▘▘▘▘▘▘▘▘▘▘▘▘▘▘▘▘▘▘▘▘▘▘▘▘▘▘▘▘▘▘▘▘

With 12V power connected, the CPU1 STATUS led should flash at 1 flash per second, and if the
intercom line is selected and offhook, CPU2 STATUS led should flash at 2 quick flashes per second.
This indicates both CPUs are operating normally.

If the status leds are NOT flashing, something is WRONG - disconnect power immediately, and refer
to the Troubleshooting section.

It is advised to use the 12VDC power supply that comes with the board which is rated 12VDC / 2 Amps.
If you use your own DC power supply, input voltage can safely range from 11.25VDC to 12.75VDC without
ill effect. 1 amp is the suggested minimum rating, up to 2 amps if you have more than 4 extensions.

1.2 - Connect 1A2 Phone Extensions

Connect the phone extensions to the card by connecting the large amphenol connectors. ___________________________________________________________________ | ::::::: INTERLINK | | EXT1 EXT2 EXT3 EXT4 | | o o o o A | | LINE1 CPU LINE2 ICM : B ╱▔▏ ╱▔▏ ╱▔▏ ╱▔▏ | | STATUS STATUS STATUS STATUS : : ▏ ▏ ▏ ▏ ▏ ▏ ▏ ▏ | | : : ▏ ▏ ▏ ▏ ▏ ▏ ▏ ▏ | | o CPU2 : : ▏ ▏ ▏ ▏ ▏ ▏ ▏ ▏ | | STATUS : : ▏ ▏ ▏ ▏ ▏ ▏ ▏ ▏ | | : ▏ ▏ ▏ ▏ ▏ ▏ ▏ ▏ | | ___ __ ____ ____ ╲_▏ ╲_▏ ╲_▏ ╲_▏ | | | | |+-| |oooo| |oooo| | |__|___|____|__|____|____|_____________|____|_______________________| Line1+2 12VDC Ring Trig Ext ▲ ▲ ▲ ▲ (RJ-11) 1.5A Connector Ring ╱┃╲ ╱┃╲ ╱┃╲ ╱┃╲ Gen ┃ ┃ ┃ ┃ ┃ ┃ ┃ ┃ .................................... : Attach extensions to the phone's : : large 50 pin Amphenol connectors : :..................................: IMPORTANT: When connecting phones for the first time, VERIFY the phones are internally wired as follows BEFORE connecting them: > Bells on pins 20/45 (Y-S pair) > Buzzers on pins 17/42 (Y-O pair) > Phone hybrid networks configured for diode ringing (see "Bell Wiring" below) For details on phone wiring, see below, sections 1.2.1 through 1.2.4.

+Open All

1.2.1 - Bell Wiring

Since this board uses a diode network to program ringing, bell ringing is only done on
1/2 of the AC wave. To support this, a small one wire change must be made inside each phone
to bypass the ringer capacitor that is between the K and A terminals on the hybrid network.
Paraphrasing Ed from Sundance Communications:


"For any kind of diode ringing to work, the capacitor between hybrid network terminals
A and K (inside phone) have to be bypassed. Move the wire on terminal 'K' to terminal 'A'
along with the existing wire."


So if a red wire is currently on the 'K' terminal, just move it to the 'A' terminal:

................................................................................... : : : : BEFORE : AFTER : : ------ : ----- : : ______ : ______ : : / \ : / \ : : | ▗ | : | ▗ | : : | | : | | : : \______/ : \______/ : : ┌──┘ └──┐ RED : ┌──┘ └──┐ RED : : │ ├────────────────▶ ◯ "K" : │ ├─────────┐ ◯ "K" : : │ BELL │ : │ BELL │ │ : : │ │ BLK ◯ "A" : │ │ BLK └──────▶ ◯ "A" : : │ ├─────┐ │ : │ ├─────┐ │ : : └────────┘ │ │ : └────────┘ │ │ : : │ │ : │ │ : : │ │ : │ │ : : ◯ ◯ : ◯ ◯ : : Y-S S-Y : Y-S S-Y : : (45) (20) : (45) (20) : : : : : PHONE TERMINAL BLOCK : PHONE TERMINAL BLOCK : : : : :.......................................:.........................................: Figure B. The diode ringing in-phone "K/A" wiring change needed for bells.

While you have the phone open, verify the bell's RED (+) wire is in fact connected to S-Y,
and the bell's BLACK (-) wire is connected to the Y-S wire, just like the diagram above.
If it's switched around for some reason, change the wiring to match the diagram, because polarity matters.




+Open All

1.2.2 - Extra Bell Wiring Details


Here's an illustration with actual components from a 2564 and 2565 model phone. Wiring may vary,
since used phones may have been changed before. What's shown are the factory wiring from the
Bell System Practices documentation.

Note there are at least two different bell ringer types one can encounter in these phones; the H1A
which has 4 wires (red, blk, slate, slate-red), and H1B which has 2 wires (red and blk).
The red arrow shows the wiring change for each type of ringer:





Figure B.2. The diode ringing in-phone "K/A" wiring change needed for bells.


+Open All

1.2.3 - Buzzer Wiring

Buzzer wiring is usually straight forward, and just a matter of making sure the two blue wires from the buzzer are connected to the Y-O pair on the terminal board.

+Open All

1.2.4 - 'Call Director' (2636) Extra Buzzer Wiring Details

Call Director model phones, such as the 2636 model, by default have the buzzer wired to the Y-S pair on Amphenol connector #2. This can be changed to the Y-O pair on Amphenol connector #1 by using the change shown in this diagram:

Connect the card to your telephone service. The phone source can be VoIP, XLink BT, or other "plain old telephone" compatible source. ___________________________________________________________________ | ::::::: INTERLINK | | EXT1 EXT2 EXT3 EXT4 | | o o o o A | | LINE1 CPU LINE2 ICM : B ╱▔▏ ╱▔▏ ╱▔▏ ╱▔▏ | | STATUS STATUS STATUS STATUS : : ▏ ▏ ▏ ▏ ▏ ▏ ▏ ▏ | | : : ▏ ▏ ▏ ▏ ▏ ▏ ▏ ▏ | | o CPU2 : : ▏ ▏ ▏ ▏ ▏ ▏ ▏ ▏ | | STATUS : : ▏ ▏ ▏ ▏ ▏ ▏ ▏ ▏ | | : ▏ ▏ ▏ ▏ ▏ ▏ ▏ ▏ | | ___ __ ____ ____ ╲_▏ ╲_▏ ╲_▏ ╲_▏ | | | | |+-| |oooo| |oooo| | |__|___|____|__|____|____|_____________|____|_______________________| Line1+2 12VDC Ring Trig Ring (RJ-11) Input Connector Gen ▲ Power ╱┃╲ ┃ ┃ Attach to Telco (VoIP, XLink, etc.) NOTE:
Xtreme Technologies "Xlink BT" and "XLink BTTN" are Bluetooth Gateway devices that can
interface cell phones to PTSN output over BlueTooth. It works fine to use that device as
the PTSN source, so that your 1A2 phones can work with your cellphone, both for receiving
and originating calls.


◢◤ ◢◤ ◢◤ ◢◤ ◢◤ ◢◤ ◢◤ ◢◤ ◢◤ ◢◤ ◢◤ ◢◤ ◢◤ ◢◤ ◢◤ ◢◤ ◢◤ ◢◤ ◢◤ ◢◤

WARNING:
This card is NOT approved by the FCC for use directly with analog PSTN/POTS lines
("Public Switched Telephone Networks", "Plain Old Telephone Service")

Legally it can only be attached to phone systems that use an interface of some kind,
like VoIP or like the XLink described above.

While this board IS designed to handle old analog POTS lines, THE RESPONSIBILITY
IS YOURS to connect it to public phone service without FCC approval. If you do, it is
assumed you are a hobbyist or EE technician who understands the implications.


◢◤ ◢◤ ◢◤ ◢◤ ◢◤ ◢◤ ◢◤ ◢◤ ◢◤ ◢◤ ◢◤ ◢◤ ◢◤ ◢◤ ◢◤ ◢◤ ◢◤ ◢◤ ◢◤ ◢◤

1.4 - Attaching A Ring Generator (If You Have One)

This step is optional. SKIP THIS STEP, if:


• You don't have an external ring generator


• You intend to use "BUZZ RINGING" instead, or you have your own external ringer and don't want
  the 1A2 phones' ringers to ring.


To configure a ring generator with the board, you can attach a 105VAC 20Hz-30Hz ring generator to enable
bell ringing in the 1A2 phones on the Y-S wire pair.

There are several options for supplying a ring generator:


* PowerDSINE 12v ring generator 70VAC/20Hz (can ring 3 or 4 phones using board's own 12v supply)

* Western Electric 118A Ring generator from an old 1A2 KSU

* VIKING PS-48-RGA (supplies 90VAC 20Hz at 10REN, can ring up to 30 phones)

* Other commercially available telephone "Ring Generator" or "Frequency Generator"


There are at least three ways to connect an external ring generator, depending on the type, listed below
in sections 1.4.1 through 1.4.3. The most common is to use the PowerDSINE "PCR-SIN03V12F20-C"
12V Ring Generator described in section 1.4.1 below:



+Open All

1.4.1 - PowerDSINE 12V Ring Generator

For the PowerDSINE 12VDC ring generator, this board provides a 6 pin header at JP5
for directly connecting this device.

The SIP header is located to the right of the "EXT RING GEN" connector, under and between
the large EXT1 + EXT2 connectors, and is labeled "POWERDSINE RING GEN" and "JP5":

____________________________________________________________________ | | | EXT1 EXT2 EXT3 EXT4 | | | | ╱▔▏ ╱▔▏ ╱▔▏ ╱▔▏ | | ▏ ▏ ▏ ▏ ▏ ▏ ▏ ▏ | | ▏ ▏ ▏ ▏ ▏ ▏ ▏ ▏ | | ▏ ▏ ▏ ▏ ▏ ▏ ▏ ▏ | | ▏ ▏ ▏ ▏ ▏ ▏ ▏ ▏ | | ▏ ▏ ▏ ▏ ▏ ▏ ▏ ▏ | | ___ __ ____ ____ ╲_▏ ╲_▏ ╲_▏ ╲_▏ | | | | |+-| |oooo| |oooo| JP5 ..... | |__|___|____|__|___|____|_____________|____|_________________________| Line1+2 12VDC Ring Trig. Ring ▲ (RJ-11) Input Connector Gen ╱┃╲ Power ┃ ┃ Location of PowerDSINE connector "JP5"

The PowerDSINE's 6 pin connector plug should be inserted into the JP5 header as follows.
Note the PowerDSINE's YELLOW wire should be at the LEFT.

┌────────────────────────────┐ JP5 │ ◯ ◯ ◯ ◯ ◯ ◯ │ └────────────────────────────┘ ▲ x ▲ ▲ ▲ ▲ │ │ │ │ │ │ │ │ │ │ YEL BLK RED WHT BLU │ │ │ │ │ __│_________│____│____│____│__ | | | | | | | | | PowerDSINE | | PCR-SIN03V12F20-C | | (or similar) | | | | | | | |______________________________| Figure C. Wiring the PowerDSINE via 6 pin plug to KSU board. Avoid connecting the plug in reverse, as the plug does not prevent one from doing so.

+Open All

1.4.2 - Attaching AC Powered Ring Generator (118A, VIKING, etc.)

For an old telco ring generator (like the WECO 118A or VIKING), you can wire the two Ring AC wires
to the RIGHT HAND TWO TERMINALS (labelled "105 VAC/20HZ IN") on the 4 pin EXT RING GEN connector:



+Open All

1.4.3 - 12V Ring Generator without 6 pin connector (Cambridge Electronics)

If you have a PowerDSINE ring generator with the connector cut off, or if you have a Cambridge Electronics
12V ring generator, you can wire it directly to the EXT RING GEN screw terminals as follows, leaving JP5 unconnected:

EXT RING GEN (+) (-) (~) (~) ┏━━━━━━━━━━━━━━━┓ ┃ ┃ ┃ ┃ ┃_______________┃ _ _ ______________┃ _ _ _ _ ┃_______________ _ _ ┃(\) (\) (\) (\)┃ ┃ ▔ ▔ ▔ ▔ ┃ ┗━━━━━━━━━━━━━━━┛ | | | | | | | | RED BLK WHT BLU | | | | | | | | _____|___|___|___|_____ | | | YEL|------ (tape off, do not connect) | | | | | PowerDSINE | | PCR-SIN03V12F20-C | | | | | | | |_______________________| Figure D. Wiring the PowerDSINE to screw terminals.

For the PowerDSINE, RED/BLK wires are +12/GND outputs to power the device from the board, and WHT/BLU wires
are AC ring outputs from the device to the board. Leave the YEL wire ("inhibit") unconnected.

For the Cambridge Electronics device, wire the +12/GND inputs to the left-hand screws on the EXT RING GEN connector,
and wire the AC output to the right-hand screws.

If you have trouble getting one or more extensions to ring, check the Troubleshooting section below.

There are two sets of 8 dip switches at the bottom of the board, SW1 (left) and SW2 (right):


Buzz Ringing -- SW1
If you don't have a ring generator, this board can still "ring" the phones using the phone's
built-in buzzers. Assuming your buzzers are wired to the 17/42 wire pair in each phone (Y-O pair),
TURN ON the appropriate DIP switches under the "BUZZ CALL" section (SW1). The 12VDC supply will handle
buzzing the buzzers during ringing.

Bell Ringing -- SW2
If you have a ring generator attached (step #4) and want the phone extensions to ring, turn on the
appropriate DIP switches under the "BELL CALL" section (SW2).


If you don't want the phones to buzz or ring during incoming calls, such as if you have your own
ringing system (bell boxes, etc), then you can turn off /all/ the DIP switches for SW1 and SW2,
and leave any ring generator connection unconnected.

Note that for each switch turned ON, it enables ringing for a particular line on a particular extension.
The first two switches manage the phone on EXT1, the second two manage EXT2, etc. Here's a full breakdown:

BELL CALL ┏━━━━━━━━━━━━━┓ ┃ off on ┃ ┃ 1 ────██ ┃ ◁── Rings EXT1 if call on Line #1 ┃ ┃ ┃ 2 ────██ ┃ ◁── Rings EXT1 if call on Line #2 ┃ ┃ ┃ 3 ────██ ┃ ◁── Rings EXT2 if call on Line #1 ┃ ┃ ┃ 4 ────██ ┃ ◁── Rings EXT2 if call on Line #2 ┃ ┃ ┃ 5 ────██ ┃ ◁── Rings EXT3 if call on Line #1 ┃ ┃ ┃ 6 ────██ ┃ ◁── Rings EXT3 if call on Line #2 ┃ ┃ ┃ 7 ────██ ┃ ◁── Rings EXT4 if call on Line #1 ┃ ┃ ┃ 8 ────██ ┃ ◁── Rings EXT4 if call on Line #2 ┃ ┃ ┗━━━━━━━━━━━━━┛ SW2

This switch arrangement is the same for both SW1 (Buzz Call) and SW2 (Bell Call).
Any switch that is "OFF" causes the line/extension combo to not ring.


So if you only want Line #1 to ring all extensions, only turn on switches 1,3,5,7.

1.6 - Testing Your Setup For The First Time

With the above "Setup" steps completed and power applied, you should now be able to test the phones.
Try these tests, in order:

1.6.1 - Intercom Test


1. Pick up the handset on a phone extension, and press the RIGHT-most line button
   to use the intercom on Line #5.


2. The lamp for that line should light on all the extensions.


3. Try dialing "1". It should buzz the phone plugged into EXT1 on the card.
   Dial "2" to buzz the EXT2 phone, etc.


4. While you're using the intercom line, have someone else pickup the same line
   on a different extension. You should both be able to talk to each other clearly
   over the intercom line.



1.6.2 - Call Test



1. Try calling Line #1's phone number from a cell phone, or another line.
   If configured, the ringers should ring, and the Line #1 lamp should
   flash at a 1 second rate. (See the Troubleshooting section for problems)


2. Answer the call by selecting Line #1 on the phone, and picking up the
   handset. The lamp should stop blinking and stay on steady.


3. Try putting the call on hold by pressing the red HOLD button.
   The Line #1 lamp should flash quickly, indicating the call is now on HOLD.
   You can now hangup and the call will remain on HOLD until you, or someone at
   another extension picks up the call.



If you don't have a live phone network configured, you can force ringing using the
"Ring Trigger Connector" by shorting the two left terminals to ring line #1, or the
right two terminals to ring line #2:

Ring Trigger Connector Line 1 Line 2 Ring Ring _____ _____ / \ / \ _ _ _____________________________________________________ _ _ | ◯ ◯ ◯ ◯ | |_________________| ▲ ▲ ┃ ┃ ┃ ┃ <-- Briefly jumper with a wire ┃▁▁▁┃ or doorbell switch to ring line #1

To ring Line #1, connect LEFT two screw terminals on Ring Trigger Connector together briefly with a
wire jumper or doorbell type switch.

To ring Line #2, do the same with the RIGHT two terminals.

This is useful for demos, where you want to demonstrate ringing with just power, but no phone line.

If you have trouble getting ringing to work, see the Troubleshooting section below entitled "No ringing".

2.0 - Using Your 1A2 Multiline Phone System

Each multiline phone has "line select" buttons to let you pick which phone line you can use.

2.1 - Hold
From left-to-right, the first button is the red HOLD button, which lets you put calls on Hold.

To use it, while a call is in progress, press and release the HOLD button to put that call on Hold.
The button will pop up and the line lamp will start winking at a fast rate indicating the line is on Hold.
Now you can either return to the call by picking up the line again, or you can use the intercom to tell
someone else the call is for them so they can pick it up.

2.2 - Line Buttons 1-5
Next to the red button are the line buttons; the first being Line #1, Line #2, and so on,
the last line being Line #5, which is the Intercom Line on this board, described below.

Each phone also contains a bell ringer and a buzzer. Depending on how your system is set up,
typically the phones "ring" when there's an incoming call, and "buzz" when someone wants you to
pickup the intercom line to talk. (See "Using The Intercom" below)

2.3 - To Make A Call
To make a call, push an available line button (that is not already lit). Choose the line button
BEFORE picking up the handset, so you don't accidentally pick up a call that is in use.

Now lift the handset. The line's button should light up on all extensions, indicating you're using the line.
You should hear dial tone.

Dial your call normally, and hang up when you're done. When you hang up, the line's light will go off
on all phones, indicating the line has freed up and can be used for new calls.

2.4 - Putting Calls On Hold
You can put an active call on hold by pressing and releasing the red HOLD button.

Once on hold, the line's lamp should "wink" at a fast rate, indicating the call is on hold.
You can then hang up the phone, and the call will remain on hold.

Any extension can then pick up the winking line to return from hold and continue the call.

If the remote caller hangs up while they are on hold, the light will go out, hold will be released,
and the line will be free for use again.

2.5 - Incoming Calls
When a call comes in, the extensions programmed to ring should ring, and the lamp for that line
should flash slowly on all extensions, indicating which line is ringing.

Phone extensions should either ring or buzz, depending on how the phones are programmed to ring.
(See "Ring Programming" under "Setup").

2.6 - Using The Intercom
The intercom is a way for people in the office to "inter-communicate", such as if a receptionist wants
to notify someone at another extension there's a call for them, or if one person wants to briefly talk
to another.

To use the intercom, push the Line #5 button, and dial the number of the extension you want to talk to.
Dialing "1" will buzz the buzzer for that extension (EXT1). If a person is available at that extension, they can
pick up the intercom line to talk to you. Dialing "0" buzzes all extensions.

If your phone buzzes, and the intercom line is lit, it means someone wants to talk to you, so pick up
that line to talk to them.

3.0 - Phone System Accessories

3.1 - Ordering Phones
To order more phones, check Ebay, Amazon, or other surplus sources for 1a2 multiline phones.
AT&T 1A2 models 565, 2564, 2565, and 2830 all have been tested to work with this board.
Other models may work as well; check the Bell System Practices (BSP) wiring diagrams to make sure.

3.2 - Ordering Extension Cables
Extension cables for 1a2 phones are available in a large variety of lengths, from short 5 foot extensions
to long 100 foot cables or more.

Practically, it's best to purchase several 25' cables than one long cable, as they can be chained together
easily if need be to attain longer lengths for flexibility.

Extension cables need male connectors on one end, and female on the other; male end connects to the control card,
female to the phone's own cable.

These cables tend not to be cheap, as they have many conductors and the connectors are industrial quality.
Prices vary between $1.00 and $2.00 per foot.. so a 25' cable might be as much as $40. (2018 prices).

There are many sources for these cables, used or new, including ebay and Amazon. Search terminology for these
cables vary:



• RJ21 telco cable
• Amphenol telco cable
• Cat3 25 pair telco cable
• Cat3 50 conductor telco cable
• 26AWG UTP Telco 25PR

You can use punch blocks with amphenol connectors to punch down cable wiring yourself. The cable can be multiple
runs of 8 conductor Cat3, Cat5, or other telecom compatible UTP (twisted pair) cable.

3.3 - Cable Terminology



• "RJ21" refers to the 50 pin amphenol connectors.


• "Cat3" refers to the twisted pair rating for voice communications,
  where the pairs of wire are twisted around each other in specific
  ways to prevent electrical noise from getting into the voice circuit
  over long runs of wire. I believe higher category numbers, such as
  Cat5, Cat6, etc. should also be OK for old 1a2 wiring, but check
  around for verification.


• "UTP" stands for "Unshielded Twisted Pair", which is typical of
  telephone cables for noise reduction.


• "25PR" means "25 pairs" of wire inside the cable, or 50 conductors total.


• "AMP" or "Amphenol" refers to the connector ends.


• M/F, F/M, F/F, M/M refer to the connector types at either end of the cable.
  You only want M/F or F/M (they're the same thing):
  
  
  
  • M/F or F/M refer to Male/Female connector ends
  • F/F refers to Female/Female connector ends (you DON'T want these)
  • M/M refers to Male/Male connector ends (you DON'T want these)


Be sure to get Male/Female ("M/F" or "F/M") connector ends on your extension cables.

Conductors can be solid or stranded; typically stranded is more flexible, as solid core wire is "stiff".

3.4 - Ring Generators
An external ring generator is required to offer the option of ringing the bells in the 1a2 phones.

Note bell ringing is not required: phones can still be "rung" using the "BUZZ CALL" option,
which if configured will "ring" the phones using the 1a2 phone's built in buzzers.

Since this board uses a 12VDC supply, the "PowerDSINE" PCR-SIN03V12F20-C 12 volt ring generator works well.
While no longer manufactured, they're still only about $15 ~ $20.00 on Amazon/Ebay.

During ringing of 4 lines, it seems to use about 500mA (0.5A), so make sure your 12vdc power supply can supply
at least 1.5A, as the rest of the card uses less than 1 amp under full load of 4 extensions + 2 lines.

Another manufacturer is Cambridge Electronics, which sells a similar 12volt ring generator called the "Black Magic".

Or, you can use any of the old telco ring generators that provide ~70-105 VAC, 20-30Hz ring voltage like the 118A.

If you have two boards, you can connect them together with a 30 pin ribbon cable to create
a single phone system with 4 Telco lines and up to 8 extensions that all can be individually buzzed on
the intercom line (by dialing "1" through "8", or buzz all of them by dialing "0").

For info on how to configure two boards with the INTERLINK connector, refer to this page which includes
diagrams and descriptions: http://seriss.com/1a2-ksu/rev-g1/data/1a2-REV-G-0015.png

In short, connect the two boards together by their INTERLINK connector using a 30 pin ribbon cable, and power
the two boards either with separate power adapters, or a single adapter of suitable amperage wired in parallel.
What follows is the recommended cabling:






This arrangement prevents obscuring the board, so one can easily see the DIP switch and jumper configurations.
Note how in the correct arrangement, the cable does a full 360 degree flip over itself, as shown in this side view:




Recommended interlink cable configuration for final installs.



One can also trivially route the cable straight across the top of the two boards as shown below without a twist,
useful for quick/simple tests:




Simple cable arrangement OK for quick tests, but obscures top board's settings.


..but that blocks access to jumper/DIP switches, so the previous arrangement is preferred, especially for final installations.

Configure one board as the "PRIMARY"; that board's telco inputs will appear as LINE 1 and LINE 2 on the extensions.
Configure the other board as the "SECONDARY"; that board's telco inputs will appear as LINE 3 and LINE 4 on the extensions.
The PRIMARY board's intercom circuit will manage the intercom line for all 8 possible extensions.

To configure the PRIMARY board, make sure all the jumper blocks are all installed on the PRIMARY jumper (JP3),
and none on the SECONDARY (JP4). Plug the Telco lines that should be LINE 1 + 2 into this board.

To configure the SECONDARY board, make sure all jumper blocks are installed on the SECONDARY jumper (JP4),
and none on the PRIMARY jumper (JP3). Plug the Telco lines that should appear as LINE 3 + 4 into this board.

Plug up to 8 extensions into the two board's EXT# connectors.

When someone picks up the intercom line, dialing 1-4 will buzz the extensions on the PRIMARY board, EXT 1-4 respectively.
And dialing 5-8 will buzz the extensions on the SECONDARY board, EXT 1-4 respectively.

Note that connectors EXT 1/2/3/4 on the SECONDARY board will really be EXT 5/6/7/8, so you may want to relabel
the connectors on the SECONDARY board.

5.0 - Troubleshooting

This section should help you solve the various problems you can have during setup, or when things go wrong.
Email erco@seriss.com if you encounter problems not defined here, esp. if you've found a solution and think others
would benefit from it.

5.1 - PROBLEM: Can't dial with Touch-Tone.


A common problem is TouchTone dialing won't work to dial out on Line #1 or Line #2; pushing buttons generates no tones,
or very low volume tones, but dialing on the intercom works fine.

Things to check:



• Check the telco line polarity.
  
  Many of the old Touch-Tone dial pads are sensitive to line polarity, so be sure it's right.
  If necessary, flop the wires at your jack.
  
  Beware some female/female RJ-11 adapters and/or RJ-11 cables are wired to swap Tip/Ring.
  So even though the jack may be wired correctly, the wire or adapters between the jack and KSU
  might be causing the swap problem.
  
  If Tip/Ring are swapped, these TouchTone pads either won't dial at all, or will put out very low
  volume tones.



5.2 - PROBLEM: Can't use Rotary to dial extensions on the intercom line



To buzz extensions with the intercom rotary dialing, only the dialing phone can be offhook. Rotary dialing doesn't
work if other extensions are offhook during dialing.

Rotary on the intercom line is supported by REV F boards (and higher) only. Older boards (REV-E, REV-B..)
do not support it.

Rotary on the regular telco lines should work regardless of board versions IF the telco equipment supports it.
Not all modern telco equipment supports rotary.


5.3 - PROBLEM: Line #1 works, but Line #2 does not



You've confirmed your jack has an active Line #1 and Line #2, but Line #2 doesn't work when connected to the KSU.

Things to check:



• Check the telephone cable you have connected between the jack and the KSU, and verify
  it's a 4 conductor wire, and not just 2.
  
  Some phone cables only have 2 conductors, the RED/GRN pair (line #1), and omit the YEL/BLK pair (line #2),
  which would cause this problem.
  
  Closely look at the RJ-11 connectors on your cable; if you only see RED/GRN and don't see YEL/BLK,
  replace the cable with a 4 conductor cable instead.



5.4 - PROBLEM: Picking up a line lights lamps but gives no dial tone



Things to check:



• Make sure the 50 pin connectors between the KSU board and the extensions are fully seated,
  and not partially connected. It's often easy to have one side of the connector or the other popped up,
  not making a full connection.



5.5 - PROBLEM: Lamps don't light when picking up a line


Things to check:



• Verify the telephone line connection.
  If there's no voltage on the telco connection, the line sensing won't activate and thus the lamps won't light.


• Make sure the 50 pin connectors between the KSU board and the extensions are fully seated,
  and not partially connected.


• Verify the CPU STATUS light is blinking. If it's not, then try "rebooting" the card by turning it on and off again::
  
  
  
  1. Pull the power connector from the board, wait a few seconds, and plug it back in again.
  
  
  2. The CPU STATUS light should be blinking. If it's not, the board may need servicing.



5.6 - PROBLEM: No ringing


One or all extensions aren't ringing with their bells during incoming calls, or when using the
RING TRIGGER CONNECTOR (as described in the "CALL TEST" section above).

Things to check:



• Verify bells of EACH 1A2 extension phone are attached to the Yellow-Slate wire pair (pins 20/45).


• Make sure the 1A2 connectors are all pressed down and seated fully. A half-seated connector can cause lack of ringing.


• Make sure the "BELL CALL" DIP switches (SW2) are set to "on" for the lines/extensions you want to ring during incoming calls.


• Make sure the external ring generator is attached correctly and verify AC ring voltage is present during the ring cycle.
  
  An external ring generator must be attached to the card for the extensions to ring by their bells.
  If a PowerDSINE is attached to JP5, verify it's not partially seated on the pins, and is not plugged in reverse.
  When positioned correctly, the YELLOW wire will be at the LEFT:
  
  
  POWERDSINE RING GEN ┌────────────────────────┐ JP5 │ ◯ ◯ ◯ ◯ ◯ ◯ │ └────────────────────────┘ YEL x BLK RED WHT BLU
  
  Refer to "Figure C" and "Figure D" near the top of this document for more info.


• For bell ringing to work properly with the diode oriented ring circuit for this board, verify all the 1A2 phones
  have the following one wire modification. Paraphrasing Ed, from Sundance Communications:
  
  
  "For any kind of diode ringing to work, the capacitor between network terminals A and K
  (inside phone) have to be bypassed. Move the wire on terminal 'K' over to terminal 'A'
  along with the existing wire."

The wire he's referring to is usually the actual bell's red wire.


• 1A2 phones typically have ringers with a single bell + clapper. These ringers are sensitive to polarity
  when mixed with a diode ring circuit. If the ringer is not ringing or barely ringing/humming, inside the phone
  try switching the two wires from the bell and the network hybrid to see if the bell's polarity is the problem.


• Note that the 12V output on the "RING GEN POWER" connector only outputs 12V during actual ringing.
  This keeps the power off for the ring generator when the phones aren't ringing.
  
  To test ringing without a PTSN network, see "Call Test" above, using the RING TRIGGER CONNECTOR
  to easily trigger ringing.



5.7 - PROBLEM: Buzz-ringing not working.


This card features "buzz ringing", where the buzzers buzz in place of bell ringing during incoming calls.
This is useful if you don't have a ring generator.

Things to check:



• Make sure the buzzers are all wired to pins 17/42 (Y-O pair).


• Make sure the 1A2 connectors are all pressed down and seated fully. A half-seated connector can prevent
  the buzzers from working, while other features work fine.


• Make sure the "BUZZ CALL" DIP switches (SW1) are set to "on" for the lines/extensions you want to buzz
  during incoming calls.


5.8 - PROBLEM: Cpu Led Not Flashing


Things to check:



• Verify the power supply voltage being fed to the board: Put a meter across the two "12V INPUT" terminal screws
  and verify +12 volts DC is being fed to the board, positive on the left screw, negative on the right.
  Voltage can range 11.5V to 12.75v, but closer to 12 is best.


• Ensure the power is true DC, and not "lumpy DC"; put a scope on the terminal screws to verify
  DC and not AC voltage.


• If 12V is coming into the board, check the 7805 (Q3) near the power connector, and verify 5V
  is between pins 2 and 3:
  
  
  -----_----- | (_) | |-----------| | | | 7805 | | | | | |___________| | | | Q3 | | | | | | 1 2 3 1: +12VDC input 2: Ground 3: +5VDC output
  
  
  Using a volt meter, keep the black (negative) lead on pin 2 during the following: touch the red lead
  to pin 1 should show +12VDC. Moving the red lead to pin 3 should show +5VDC.


• Check the temperature of Q3 (the 7805 at the lower left of the board, near power connector). If it gets
  warm or hot quickly after power is connected, SOMETHING MIGHT BE SHORTED OUT - REMOVE POWER QUICKLY.
  First let it cool, then unplug all connectors, and then plug in JUST the power connector. If that corrects
  the problem, plug things back in one at a time until the culprit is determined.
  
  Also: check for any stray metal parts touching either the back of the board (stray screws, metal dust),
  or metal bits lying across any of the components on the board that might cause a short.
  
  Keep in mind stray metal/liquids lying across components may have permanently damaged the board to the point
  where components are blown, and may need to be swapped out to properly repair the board.


5.9 - PROBLEM: Hitting HOLD causes line lamp to turn off instead of flash


Check to make sure the line isn't dead. Without talk battery from the CO, the line can't go into Hold.

In the v1.5b firmware, the line lamp comes on during pickup whether the line is alive or not.
This is so that pressing RECALL (for phones that have this feature) or use rotary dialing doesn't
flash the line lamp.

But if the line is inactive, the line can't go into Hold because there's no line current.

Bell System Practices wire color codes are used throughout this document,
e.g. Y-S and Y-O. The color codes are:
R - Red G - Green BR - Brown W - White O - Orange BL - Blue BK - Black Y - Yellow V - Violet S - Slate Mostly single letters are used, but where confusion might arise, two letters are used (like BR for brown,
BK for black, BL for blue). To avoid confusion with green (G), gray wires are always referred to as "slate" (S).

In telephone wiring, CAT-3 UTP cable (Category 3, "Unshielded Twisted Pair") is used to ensure long runs of signals
have the best noise cancellation, such that each voice circuit is on its own pair of wires that are physically
twisted together. Most 1A2 phones have 25 pair (50 conductor) CAT-3 UTP cables.

Each pair of wires twisted together share the same two colors, just swapping which is the "main" or "primary" color;
The "Y-S pair" (yellow-slate) consists of two wires:

Y-S -- A mainly yellow wire with a slate (gray) stripe ▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄ S-Y -- A mainly slate (gray) wire with a yellow stripe ▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄ So it matters which color appears first; When referring to a *single wire*, the first of the two colors is always
the "main" (or "primary") color, and the second color is the stripe's color. So in Y-S, Y is the primary color,
and S is the stripe.

When referring to *wire pairs*, the first letter is the main (or "primary") color GROUP. In a 25 pair CAT3 UTP cable,
wire pairs are broken into 5 color groups of 5 pairs each:

25 Pairs / 5 "Color Groups"
WHITE GROUP W-BL ▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄ ⎤ W-BL BL-W ▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄ ⎦ Pair W-O ▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄ ⎤ W-O O-W ▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄ ⎦ Pair W-G ▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄ ⎤ W-G G-W ▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄ ⎦ Pair W-BR ▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄ ⎤ W-BR BR-W ▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄ ⎦ Pair W-S ▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄ ⎤ W-S S-W ▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄ ⎦ Pair
RED GROUP R-BL ▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄ ⎤ R-BL BL-R ▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄ ⎦ Pair R-O ▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄ ⎤ R-O O-R ▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄ ⎦ Pair R-G ▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄ ⎤ R-G G-R ▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄ ⎦ Pair R-BR ▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄ ⎤ R-BR BR-R ▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄ ⎦ Pair R-S ▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄ ⎤ R-S S-R ▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄ ⎦ Pair
BLACK GROUP BK-BL ▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄ ⎤ BK-BL BL-BK ▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄ ⎦ Pair BK-O ▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄ ⎤ BK-O O-BK ▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄ ⎦ Pair BK-G ▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄ ⎤ BK-G G-BK ▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄ ⎦ Pair BK-BR ▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄ ⎤ BK-BR BR-BK ▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄ ⎦ Pair BK-S ▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄ ⎤ BK-S S-BK ▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄ ⎦ Pair
YELLOW GROUP Y-BL ▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄ ⎤ Y-BL BL-Y ▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄ ⎦ Pair Y-O ▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄ ⎤ Y-O O-Y ▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄ ⎦ Pair Y-G ▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄ ⎤ Y-G G-Y ▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄ ⎦ Pair Y-BR ▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄ ⎤ Y-BR BR-Y ▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄ ⎦ Pair Y-S ▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄ ⎤ Y-S S-Y ▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄ ⎦ Pair
VIOLET GROUP V-BL ▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄ ⎤ V-BL BL-V ▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄ ⎦ Pair V-O ▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄ ⎤ V-O O-V ▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄ ⎦ Pair V-G ▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄ ⎤ V-G G-V ▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄ ⎦ Pair V-BR ▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄ ⎤ V-BR BR-V ▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄ ⎦ Pair V-S ▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄ ⎤ V-S S-V ▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄ ⎦ Pair


So when referring to *wire pairs* in the "yellow group", the "Y" is always specified first, e.g.
the "Y-S pair" (not the S-Y pair), and the "Y-O pair" (and not the O-Y pair).

In this document, the Y-S and Y-O pairs in particular are referenced a lot, because they're used by the KSU
for Bells and Buzzer respectively, as often the wiring for those needs to be checked and changed.