atcomsystems.ca/forum Forums Other TDM Phone Systems 1A2 and Comkey Telephones & Systems Greetings and a Request for Some Info on How to Setup Small Keyset System

There's nothing wrong with your lamp grounds being tied together in the set as long as you maintain proper polarity. I swear that your KSU and cable are on the way. I am surprised you haven't received them yet.

Okay, you woke me up.....565 came first .... 564 was an upgrade.....either way will work UNLESS you need the extra pairs....look at a print on the 10 button set to see what I mean.

Now let's confuse the situation....WECO 851 AIM.

Well, sort of...

Actually, it's two and a half pairs per line key, of which there are 9, whether they are used for CO/PBX or ICM service.

(The unused "balance" leads of line keys 2, 3, 4 & 5, generally left insulated and stored in a 56X-series phone, are used as the "A" leads for line keys 9, 8, 7 & 6, respectively.)

So, counting the conductors, we have:

T,R,A,LG,L times 9 keys is 45 conductors.

A1 ground = (Orange/White) = 1 conductor

Ringer pair (Yellow/Slate) = 1 pair = 2 conductors

Buzzer pair (Yellow/Orange)= 1 pair = 2 conductors

Total conductors = 50

In a Western 2830 set, the lamp grounds for line keys 1 through 7 are dedicated to mounting cord conductors. (In ITT sets, I seem to recall that the lamp grounds were "bunched" on terminal screws, allowing them to be separated and used for other applications.) The last two lamp pairs (LG & L leads for line keys 8 & 9) and their associated mounting cord leads are connected on terminal screws inside the set, so that they can be moved and used to provide the four leads needed for 3-type speakerphone service, (T1, R1, 1T & 1R) in the absence of a separate cord between the set and the 55-type control unit. If the control unit is hidden in a wiring closet, the mounting cord leads are used, because the assumption is that the 25-pair cable is threaded through walls and ceilings, back to the equipment. If the control unit is stuck under the victim's desk, then a separate 10-conductor cord could be used to provide the leads.

If common bell cut-off was specified, the Y/Sl leads could be re-routed in the closet through the K1 relay contacts in the 55-type control unit, or they could be fed through extra conductors in the 10-conductor cord at the desk location.

I often ran a 25-pair and an extra 4-pair in places in offices that seemed likely to need a few more pairs, especially if the cables were being run in conduits. The amphenol hung out of the wall plate, and the 4-pair was left coiled inside the wall, where it could be terminated later on a 44A block or whatever piece of equipment for which it was required.

This turned out to be a good idea in offices where the system was migrated to a ComKey 416 system, which required that the CO T&R feeds be fed to the primary stations on separate pairs. (i.e. not stealing the Violet leads)

The ground returns for the ringer and the buzzer could use the A1 ground, in a pinch, and that would also provide an extra pair. The unbalanced condition of using half-pairs for ringer and buzzer did not cause any appreciable cross-talk on relatively short runs (under 100 feet) from the set to the closet, where the unbalance was corrected to a balanced pair via the cross-connection field.

What are ground returns? Do I want to know?

Ed,

I think they arrived today, but I wasn't home to collect, so the post office left me a notice of delivery. I'll go pick them up at the post office tomorrow.

The 564 came after the 565!? <scratching head>

Could someone give me a run down the role played by the "A" leads? If I understand correctly, they are the control pair for the line, but what exactly is being controlled? Lamp flashing? Sorry for the ignorance! HA!

A leads actually do several things: When just going off-hook, they close a relay causing the line's lamp to light. This is done by a ground being placed on the line's A lead.

If the line is in use and the ground is removed from the A lead, it causes another relay to operate placing a high-resistance short on the line to hold it and changes the lamp from steady to winking.

On an incoming call, when going off-hook, the A lead also stops the incoming ringing that is usually generated within the KSU unless bridged CO line ringing is being used.

Note that all relays mentioned are components of the line card itself. The KSU does not have any "intelligence" at all. The only electronics to speak of are within the power supply.

The interrupter is also a part of the KSU which is a motorized contact switcher providing flashing lamp, winking lamp (hold) and interrupted ringing. The motor in the interrupter is under control of any line card in the system that seeks these services.

Jeff: "Ground return" simply means the wire that completes a circuit from a device that had a "hot" lead activating it. For instance, the 10 volt AC lamp supply goes to the lamp, through the lamp, and back to system ground. That's the ground return for that lamp.

Cat6: The 564 predated the 565 by several years.

The "A" lead is one of three leads that are switched when a line key is depressed. (We say "key" rather than "button" because historically, people operated keys, going back into the days of telegraphy. Buttons are those little things that are on a TT dial or hold your shirt together. That's why these things are called "key" systems.)

The line key makes three leads: the Tip, the Ring, and the "A" lead. You know what the T & R do, and the third contact on the line key operates the A lead, which takes A1 ground (present in the tel set on the O/W lead, via the break contact on the HOLD key,) and sends the ground via the switch-hook and the A lead to the line circuit relay associated with that line. This relay can be part of a hard-wired group of relays (as in 1A1 systems) or on a 400-series printed circuit line card (in 1A2 systems.) The line relay operated sends lamp battery to the lamp lead of the line on all sets, and prepares the HOLD circuit. When the sub hangs up, the A lead opens, and the relay falls, releasing the line lamps. If the sub presses the HOLD key, the A ground is released just before the T&R are released, due to the mechanics of the HOLD key/line key linkage, and the line circuit starts the interrupter, switches the lamp lead from steady supply to wink supply, and the line lamp indicates a HELD line by the winking lamp. (120 ipm). On an incoming call, when the sub presses the line key and goes off-hook, the A lead serves as a supervisory lead, tripping the ring, changing the lamp supply from flashing (60 ipm) to steady.

Got it now?

Thank you Ed and Arthur for that I will have to slowly read through both posts several times to get a firmer grasp, but my understanding of the concept is losing some viscosity

Ed,

I knew the KTU is the "brains" behind the operation so to speak