sundance-communications.com/forum Forums Other TDM Phone Systems 1A2 and Comkey Telephones & Systems Network Terminal Designations

Hello all. Been a long time since I posted. Been busy with work and school.

I have a question. I replaced a touch-tone dial on a wall mount WE phone the other day, and was curious as to what the terminal designations correspond to.

There was:

RR
R
G
Gn
B
C
F
S
T
L1
L2

It would be good to know what functions these terminals serve.

I think F is hook switch.

Thanks!

RR: Input from the switch hook for the tip side;

C: Input from the switch hook for the ring side;

R: Common output to the handset for both the transmitter and receiver;

B: Output to transmitter (returns to R)

GN: Output to receiver (returns to R)

G,F,S,T,L1 and L2: Blind terminals used to connect ringer, dial, handset, and/or switch hook leads together. There isn't anything inside the network connected to these terminals.

Terminals S and T are only necessary where a touch-tone dial is present, but any blind terminal will suffice.

To sum it up:

Tip/ring input to the network is via terminals RR and C, while the output to the handset are via terminals GN and B, sharing terminal R as the common between the transmitter and receiver. It is the type of dial that makes it look more complicated. Touch-tone dials have a lot of "in and out" connections.

You are correct in assuming that terminal F is from the green (or white) switch hook lead and it is usually a tie point to connect to the green dial lead. This differs between brands and also between single-line vs. multi-line sets.

Also, terminals A and K have the ringer capacitor placed across them, just in case you are interested.

Ed -

Excellent!

Sam

scary thing is it was probably from memory

'Fraid so, Skip. Come sit on the porch with me (full cooler required) and I'll tell you all you want to know. I love this stuff.

Ed, my cousin is a Coors sales rep. Name the date and time and I'll join in!

Damn!!! Good stuff Ed! Thanks a million!

I was reading an article somewhere about the "lost art of 1A2". The article literally referred to it as that. They should hire you as a consultant!

Actually, F is not a blind connection.

There is a network (phone company lingo for any combination of resistors, capacitors and/or varistors) between F and RR to inhibit dial pulse corruption. It is a resistor/capacitor series network from F to RR, and there is a varistor at the center tap of those components going to C.

Yeah, I know but I didn't think it was really significant. I was just generalizing about the terminal functions from a hobbyist's perspective.