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Monday
Oct212013

NuTone IK15 and IK25 DoorCom Entry Intercom Systems

“Know who's at your door before you open it with NuTone's easy-to-install IK25 Surface-mounted DoorCom. It's a melodious 2-note electronic chime. . . with intercom capability!”

Two Inside Speakers provide the security and convenience of answering the door without opening it from two locations. . . plus private intercom between the inside speakers.

 

NuTone introduced the IK25 DoorCom system in 1975 and it remained in production until 2010.

 

The IK25 DoorCom was a prepackaged “kit” intercom system. The kit included the 2 inside stations, 1 entry door speaker and a low-voltage transformer, everything you need to install the IK25, except for the wiring.

The 2 inside stations look identical, but they are very different from each other. 1 of the inside stations would be considered the “Master Station”, it contains all of the electronics that enable the system to operate. This Master Station is the hub of the IK25 System and all of the other components of the system wire directly back the this Master Station.

The second inside station is just a decorative plastic grill which contains a speaker cone and 2 push button switches. In a standard installation (without an electric door release), a 5-conductor cable is required between this remote station and the Master Station.

The Entry Door Speaker is a small brown plastic station which includes a Door Chime Push Button and a Name Plate. This IS68 Entry Door Speaker is unique to the IK25 and the IK15 DoorCom Systems. The design feature that make the IS68 different from all other NuTone Door Speakers is that it only requires 2-wires (1 pair) for both the chime operation and voice communication (all other NuTone Intercom Systems require 4-wires (2 pairs) to accomplish these functions.

The final piece of the IK25 Kit is the Model 101NA low-voltage transformer. The 101NA is rated at 16 volts AC @ 10 watts. This is a fairly small, low power transformer, however since the IK25 is an all electronic system, it doesn't require much power to operate.

There were only 2 optional items available for the IK25 system. You could add 1 additional IS68 Entry Door Speaker to the system and there was also an optional Electric Entry Door Release (DR1 or DR2). When the Door Release option was used, it was necessary to add 1 additional push button to each of the inside stations (2 buttons total). The additional inside push buttons were model IM25SW and they matched the standard rectangular buttons on each station.

The Door Release function was already built-in to the IK25, so it was just a matter of adding the extra push buttons and connecting the additional wiring inside the station. It was also necessary to install another pair of wires from the Master Station to the Electric Door Release Mechanism in the entry door frame.

It was recommenced that genuine NuTone Electric Door Releases be used. The DR1 was designed for doors with wooden frames and the DR2 was designed for doors with metal frames. The advantage of using these door releases was that they were matched to the activation circuit inside the IK25. Using another brand or type of door release often would cause the door release circuit inside the IK25 to fail, which was caused by the door release drawing to much current and damaging the IK25.

Operation of the IK25 is very straight-forward. A visitor pushes the Door Chime push button on the IS68 Entry Door Speaker, the IK25 System is activated and the Chime Tones are heard at both of the Inside Stations.

The IK25 System stays active for between 12 and 20 seconds (this is adjustable). If no one answers the door, then the system returns to its “stand-by” state.

To answer the door, the “Door Talk” button is pressed on either of the inside stations, The conversation is controlled entirely by the inside station. Simply push the “Door Talk” button to speak with the visitor and release the button the hear the reply. The speaker will “Time Out” at the preset interval once the conversation has ended.

Using the “Inside Talk” push button allows communication between the 2 inside stations. This is a private conversation and it is not heard through the IS68 Entry Door Speaker.

 

The Common Problems with NuTone IK25 System:

 

The biggest problem with the IK25 really has always been its low price. It is probably safe to guess that in the 25 years it was in production, NuTone may have manufactured 250,000 IK25's or more!

The original List Price in 1985 was $94.80 and that price increase to $184.00 by the time it was discontinued. At those price levels no one ever really repaired a IK25. It was very common to replace the IS68 Door Speaker when it failed, however if the Master Inside Station developed a problem a new IK25 Kit would be installed in place of the original system. It was just easier and a better value for the customer this way.

While there are perhaps hundreds of thousands of IK25 systems installed in homes, business and multi-family dwellings there is almost no solid documentation about the equipment itself.  There has never been any Service Manual or Electronic Schematic published for the IK25.  Even the official NuTone Parts Sheet doesn't list the circuit board in the IK25 as a separate part.

To make things even more complicated, there are probably 6 - 8 different production variations of the IK25 "Master Station".

On these pages, I'll try to shed some light on this simple but mysterious NuTone System. 

Monday
Oct212013

NuTone IS68 Entry Door Speakers

The number one problem for both IK15 and IK25 Systems are the entry door speakers.

Like any intercom equipment that's outside, it has a hard life and it will fail sooner or later. The IS68 is a unique Entry Door Speaker that is used only with the IK15 and IK25 DoorCom Systems.

What makes the IS68 unique and different from all other NuTone Door Speakers has to do with the total number of wires it needs to operate both the Door Chime Push Button (to ring the chime) and the Door Speaker (for communication).

For almost all other NuTone Intercom Systems, Entry Door Speakers require 2 pairs of wires (4-wires total) to operate both the Chime and the Speaker. One pair of wires are connected to the Chime Push Button and the other pair of wires are connected to the Speaker Cone. These 2-pairs of wires have no operational connection between them, they just happen to be connected up at the same location (but at different terminals) when the Door Speaker is installed.

The IS68 is different because it only requires 1 Pair (2-wires) for BOTH the Chime Push Button and the Door Speaker, these 2 functions share the 2 wires. NuTone designed the IK15 and IK25 this way so that these systems could be installed in place of a standard 2-note mechanical door bell system and reuse the original wiring. The IS68 would be mounted in the same spot where the original door bell push button had been located and it would reuse the same original 2-wires.

The IS68 Door Speaker is made up from the 3 basic pieces that all NuTone door speakers have. There is a plastic faceplate which has a small speaker cone attached to it and a non-illuminated push button. These 3 pieces are not really special, but how they're connect together is special.

 

In the IS68, the Speaker Cone is connected directly to the Push Button. As shown in this simple schematic drawing there are 2 capacitors that connect 1 terminal of the speaker cone to 1 terminal of the push button. The 2nd terminal of the speaker cone is connected to the 2nd terminal of the push button by a short piece of wire.

The push button also has an additional wire on each terminal. These connect back to the IK15 or IK25 Master Station.

This is a very cleaver design and it's easy to duplicate on the back of a standard, modern NuTone Door Speaker.

Since the IS68 door speaker is no longer available from NuTone, being able to modify a modern door speaker to replace a failed IS68 is a good thing.

Here's a list of what is needed to create a correct replacement for a failed IS68 Door Speaker:

1 - NBD300 Door Speaker: available in Bright Brass (BB) Antique Brass (AB) Nickel (N) or White (WH)

1 – NES300DBL Plastic Door Speaker Surface Mounting Frame (box)

2 – 100uf 35 Volt Electrolytic Capacitors (Axial capacitors are easier to work with, Radial capacitors will work just as well)