Question about hookswitch wiring (ITT 427 type network)

[MaximRecoil]

I want to use a 2500 type keypad and an ITT 427 type network in an application that has a hookswitch with just one normally-open SPST microswitch (when off-hook the switch is open; on-hook the switch is closed) as opposed to the pack of leaf switches that a normal 500 or 2500 has.

Can all 7 of the original hookswitch wires be removed from the network and just 2 wires from the microswitch be connected to the network to make it go on and off hook? I know there wouldn't be any shunting of the receiver that way, but I just need it to be able to pick up and hang up the line.

The current stock (and working) hookswitch wiring is like this:

Code Select Expand

Slate/yellow - L2
Slate        - L2
Slate/green  - L1
Slate/brown  - L2 terminal on the keypad
Slate/red    - R
Slate/white  - L1 terminal on the keypad
Slate/black  - GN
And I don't know if it matters, but the rest of the wiring is like this:

Code Select Expand

Handset cord
------------
Red     - E2
Black   - B
Green   - R
White   - GN

Line cord
------------
Red     - L2
Green   - L1

Ringer
------------
Red     - K
Black   - L1

Keypad (35A11 type I believe)
-----------------
Orange/black - C
Slate/white  - RR
White        - GN
Red/green    - R
Red          - E2

Plus the two wires from the hookswitch that I mentioned above.

[MaximRecoil]

I figured it out. First I diconnected all the stock hookswitch wires, then I connected one wire from the microswitch to the L1 network terminal and the other wire to the L1 keypad terminal. That allows the microswitch to open and close the L1 circuit.

In stock form, the L2 circuit is on a switch too, but I don't believe that's necessary (plus I don't have a second switch; I could do it with a DPST microswitch though, if I could find one that's the same form factor as the existing one), so I just ran a jumper wire from the L2 keypad terminal to the L2 network terminal.

It works, albeit, backwards right now (i.e., going on hook gives you dial tone / going off hook hangs up). Fortunately, the microswitch can be wired either as normally-open or normally-closed, so that's an easy fix.

[MaximRecoil]

In stock form, the L2 circuit is on a switch too, but I don't believe that's necessary (plus I don't have a second switch; I could do it with a DPST microswitch though, if I could find one that's the same form factor as the existing one), so I just ran a jumper wire from the L2 keypad terminal to the L2 network terminal.

Is there any importance to having a switch on both L1 and L2? With the way I have it right now, with a hookswitch just on L1, it seems to work fine, but L2 is always electrically connected to the phone line even when you hang up. Could that cause any problems?

No one seems to make a DPST microswitch in the form factor that I need (subminiature, like this one - https://www.digikey.com/en/products/detail/omron-electronics-inc-emc-div/D2S-10LD/1811978), which is too bad, because that would make it easy to switch both L1 and L2 simultaneously.

If it's important to have both L1 and L2 switched, I could add a second microswitch to the hookswitch assembly. The attached picture shows the simple mechanism. I could just get a pair of mounting screws that are twice as long as the stock ones so that I could mount a second identical microswitch right up against the one that's already there. The cam that activates the microswitch lever is wide enough to activate two of them at once.

I'd have to make some minor modifications to make it reliable though. The clear plastic sleeve that has the cam on it can shift a little from left to right; I positioned it as far as it would go to the left for the purposes of the picture, to show the width of the cam. That results in about 75% of the width of the cam being under the microswitch lever, with 25% to spare for activating a second microswitch. I'd rather have it be an even 50/50 and make it so it can't shift side to side. I'd have to shorten the sleeve a little so that it can move farther to the left, and then add a spacer (such as a nylon washer) on the right-hand side to keep it from shifting back to the right.

[poplar1]

You don't need to open both tip and ring sides of the line.

[MaximRecoil]

You don't need to open both tip and ring sides of the line.

Thanks. Do you know why Western Electric had a switch on both tip and ring that opened and closed simultaneously? Was it just for the sake of redundancy?

The reason I'm wondering if something's wrong with the wiring in this phone I put together is: when it's plugged in, my Western Electric 554 in the kitchen sounds different through the receiver when dialing. It's hard to describe, but on the dial's return, when it stops, there's somewhat of a pop sound in the receiver ("pop" isn't the best word, but I can't think of any other word to use). When I unplug this phone, that goes away (and it never did it before I put this phone together and plugged it in).

As I was typing this I figured out what's causing it, but I don't know why it's causing it. It's the little electronic "ringer" that's built into the keypad of the phone I put together.

If I disconnect the electronic ringer then the 554 is normal; if I reconnect its ringer, the 554 makes that popping sound when dialing. I also noticed that when going on or off hook, and when dialing, from any of my three plugged-in rotary phones, that electronic ringer in this phone I put together makes little chirp sounds that correspond with the hookswitch opening/closing, and it does it regardless of the polarity of its 2 ringer wires. Also, I've already confirmed that the polarity of all of my phone jacks is correct (I used a Western Electric 2500DM [no polarity guard] to test all of them).

Somehow that electronic ringer is giving/getting feedback into/from the line even when the phone it's attached to is on the hook. Its 2 wires are connected to K and L1, and the rest of the wiring is the same as I typed out in my original post, with the exception of the hookswitch wires. I disconnected all of those and connected the single microswitch to L1 like I described in reply #1.

[5415551212]

Thats interesting the electronic ringer must be affecting inductance or capacitance?
Technically it should not be necessary to switch both, especially in a two wire circuit.
Great idea with the micro switches I have a old Stromberg Carlson phone that has a hopeless hook switch I should just replace with a few micro switches.
I think in some phones the extra contact on the hook switch can be used for an A-Lead, or perhaps there are 3 sets of contacts in those cases?

[poplar1]

Do you have a jumper wire from L2 to A?

L2-----------) /---------'ringer-----------L1
               A  K
             [capacitor]

[MaximRecoil]

Do you have a jumper wire from L2 to A?

Yes, it's always had a jumper wire from L2 to A. I forgot to mention it when I typed out the wiring connections in my original post.

L2-----------) /---------'ringer-----------L1
               A  K

I'm not sure what that means. If it means L2 should be jumped to A, and the "ringer" should be wired to K and L1, then that's indeed how it's wired.

[MaximRecoil]

You don't need to open both tip and ring sides of the line.

I can see now why Western Electric put a switch on both L1 and L2 which opens and closes them simultaneously when you go on- and off-hook. I noticed today that when my phone that I put together, which only has a switch on L1, is on-hook, there remains very faint electrical noise in the receiver. If I touch the L2 terminal with my finger the noise gets slightly quieter (even though it's already very quiet to begin with). If I disconnect L2 when on-hook then of course the noise goes away completely, because the network is completely disconnected from the phone line at that point.

I think I'll do what I described in the last two paragraphs of reply #2 so that both L1 and L2 are switched like in a stock WE phone, but it's too late to go to the hardware store today to get the longer screws and nylon washer that I need. I hope they have machine screws that small.

[MaximRecoil]

I have a new plan to incorporate 3 hook switches instead of just 2, the same as a stock WE 500/2500/etc., phone has (1 for L1, 1 for L2, and 1 to mute the receiver).

That clear plastic sleeve that can be seen in the picture I posted in reply #2, is like a camshaft in an engine, except it only has one cam lobe to actuate one microswitch. If I made another cam lobe out of e.g., 1/4" thick plexiglass, and glued it in place, it could actuate two microswitches at the same time. And if I made a third cam lobe, it could actuate 3 microswitches at the same time.

The third lobe will need to be offset from the first two, so that it actuates its microswitch slightly earlier/later than the L1 and L2 microswitches get actuated, which will allow for muting of the receiver just before L1 and L2 get opened (i.e., when going on-hook), and unmuting of the receiver just after L1 and L2 get closed (when going off-hook), the same way that a stock WE phone works. The third microswitch will also have to be wired opposite of the other two, i.e., wired as normally-closed instead of normally-open.

That's the plan anyway. We'll see how it works out in reality. I've already confirmed that there's enough room in there to stack 3 microswitches together, and 1/4" is the exact width of each microswitch, so 1/4" thick plexiglass will make cam lobes that are the right width.

It will look something like this:

[MaximRecoil]

I just got the "cam lobe" made and mocked it up in there (I just taped it to the "camshaft" and the 2 additional microswitches aren't wired up yet; when I finish it will be super glued to the shaft), and it works perfectly. When I depress the hook switch lever the first microswitch actuates (which I'll wire as the receiver muting switch) and then the next two microswitches actuate (which I'll wire as switches for L1 and L2).

The receiver muting switch should be wired to the same two terminals on the network that the two receiver wires are wired to (R and GN), is that right?

I've attached a short video of it working (hookswitch.zip), along with a couple of pictures.

[MaximRecoil]

The cam lobe I made is super glued in place and the microswitches (Omron D2S-10LD) are all wired up.

The switch closest to the top of the picture is the receiver muting switch and is wired as normally-closed. The other two switches are for L1 and L2 and they're wired as normally-open.

When off-hook, all three microswitch levers are depressed by the cam lobes, so the receiver-muting switch is open (i.e., the receiver isn't muted) and the L1 and L2 switches are closed, which connects the network to the line cord.

When going on-hook, the receiver-muting switch actuates first to mute the receiver and then the L1 and L2 switches actuate to disconnect the network from the line cord, and when going off-hook, the L1 and L2 switches actuate first to connect the network to the line cord while the receiver is still muted, and then the receiver muting switch actuates last to unmute the receiver.

In other words, it works in the exact same way that a Western Electric model 500/2500/etc. hookswitch assembly works.