The lack of signals on many layouts and the scarcity of them on others leads me to believe that their expense has scared people away. For instance, after the expense of a turnout plus a Tortoise, springing for a working turnout signal as well may seem like budget busting. And indeed some individual signals are $10, $13 or more. My layout has 73 turnout signals, 3 crossbuck signals, 3 polarity warning signals, 125 lighting lamps, and 21 two-lamp block signals, in addition to 34 on/off indicator lamps on control panels. I had no desire to budget-bust to obtain these items, so I researched it and feel I got nice results. Judge for yourself.
For $1.11 you can make each turnout have a bicolor signal that's green in normal (mainline) position and red when switched (or if you'll settle for yellow and green, you can spend as little as 27¢ per signal). Get SIG 1/8" nylon landing gear clips SH-522 (fig. 1) and drill 7/64" holes through all existing holes, paint them black, and cut them as shown in fig. 2 once the paint dries. Let's call these signal lamp holders. Now get 2-lead Linrose bicolor LEDs (4301F1/5, see PARTS LIST) or 2-lead All Electronics bicolor LEDs (LED-66), ream the signal lamp holders' holes again with the drill bit—I do it by hand at this stage—to remove paint, and stuff the LEDs into the holes with the wires parallel with the bottom of the signals. Bend the wires over as in fig. 2. When installing, drill 1/16" holes in subroadbed—probably ½" plywood—but fan the holes outward a bit so you'll have room to solder under the layout.
For a cheaper red/green alternative, use All Electronics' bicolor red/green LED-67, which has three leads and needs to be wired to one of the SPDT accessory switches built into your Tortoise switch machine and powered by your 13.8-volt DC switch machine power pack—see below—and wired in with a 1.3 K resistor. See fig. 7.
If you'd prefer 2-lamp signals, there are several options: (1) Use All Electronics 8¢ red and green LEDs with cut-down Bachmann plastic HO block or dwarf signals which come on cards. (The T-1 sized LEDs are more HO-scale than N-scale, so what holds them will be a bit over scale as well.) (2) N.J. International #2100 N-scale 2-lamp dwarfs are very nice-looking and to scale (but expect to spend $12.99 each). (3) Use Tortoise's built-in accessory switches and your layout's 12-volt lighting system to power red and green glass-stained (see PARTS LIST) 3-volt Circuitron 1.4mm #7418 lamps ($1.41 per lamp in quantities of 12) with 440-ohm, ½-watt resistors soldered to one lead, and use Bachmann's #42503 Signal Bridge w/6 block signals (75¢ each) or N.J.I.'s #4203 signal heads ($2.19 each) to which you can CA your own dwarf signal bases.
I'll be concentrating now on the bicolor LEDs—which is what I recommend most strongly: To wire them in, I recommend Tortoises, 13.8-volt DC Radio Shack power packs (to run motor and LED), and wiring the LED in series with the #1 or #8 connection on the Tortoise that also powers the motor. This beats using the built-in Tortoise accessory switches because the LED needs no resistor, and this way you won't have to deal with three extra solder joints on the Tortoise. Also, the Circuitron people that build the Tortoises recommend this as a good way to do it—I asked them. Make sure you test red or green before soldering. See fig. 3.
Cheap But Effective Signals in N Scale